Netflow Overview Developed by Cisco Systems in 1996

Netflow Overview • Developed by Cisco Systems in 1996 • The value of information in the cache was a secondary discovery – Initially designed as a switching path • Net. Flow is now the primary network accounting technology in the industry • Answers questions regarding IP traffic: who, what, where, when, and how • Net. Flow version 9 an IETF standard

Traffic Analysis • What we needs – – • • • application performance application-based accounting network security Network behavior, application recognition ‘debug ip packet’ in router? IP Sniffing in shared LAN (or using switch to do so) Port Span in switch (how about port span in router? ) Circuit Sniffing Netflow What we prefer in backbone: – Embeded – Fixed length partial packet export – Real-time filtered packet export

Addressing The Needs with Netflow

Netflow Possible Applications • • • Network Monitoring Network planning Security Analysis Application Monitoring User Monitoring Traffic Engineering Peering Agreement Usage-base Billing Destination sensitive billing

What is a flow? Defined by seven unique keys: 1. Source IP address 2. Destination IP address 3. Source port 4. Destination port 5. Layer 3 protocol 6. TOS byte (DSCP) 7. Input interface (if. Index) A Flow is Unidirectional! Exported Data

Net. Flow Sequence 1. 2. 3. 4. 5. Create and update flows in Net. Flow Cache Expiration Aggregation? Export Version Transport Protocol

Net. Flow Sequence (continued) step 1 step 2 step 3 • Inactive timer expired (15 sec is default) • Active timer expired (30 min (1800 sec) is default) • Net. Flow cache is full (oldest flows are expired) • RST or FIN TCP Flag Ye No s e. g. Protocol-Port Aggregation Scheme becomes step 4 Aggregated Flows – export Version 8 or 9 step 5 Export Packet Heade r Non-Aggregated Flows – export Version 5 or 9 Payload (flows)

Netflow Processing Order Pre. Processing Packet Sampling Filtering Features And Services IP Multicast MPLS IPv 6 Post Processing Aggregation schemes Non-key fields lookup Export

Creating Export Packets Enable Net. Flow Traffic Core Network (IP, MPLS) PE Export Packets • • • Approximately 1500 bytes Typically contain 20 -50 flow records Sent more frequently if traffic increases on Net. Flow-enabled interfaces UDP Net. Flow Export Packets Collector (Solaris, HP-UX, or Linux) Application: Performance Billing Security

Net. Flow Principles • Inbound traffic only (with some exceptions) • Unidirectional flow • Accounts for both transit traffic and traffic destined for the router • Works with Cisco Express Forwarding (CEF) or fast switching • Almost supported on all interfaces and Cisco IOS Software platforms • Provides the sub-interface information in the flow records • 6500/7600 enables Netflow on all interfaces by default

Comprehensive Platform Support GSR 12000 ESR 10000 AS 5300/ 5800 3700 3600 1400/ 1600/ 1700 2500/ 2600 4500/ 4700 7200/ 7500/ Catalyst 5000/6500/ Catalyst 7600 4500

Net. Flow Versions

Version 5 - Flow Format Usage • Packet Count • Byte Count • Source IP Address • Destination IP Address Time of Day • Start sys. Up. Time • End sys. Up. Time • Source TCP/UDP Port • Destination TCP/UDP Port • Input if. Index • Output if. Index • Next Hop Address • Source AS Number • Dest. AS Number • Source Prefix Mask • Dest. Prefix Mask Qo. S • Type of Service • TCP Flags • Protocol From/to Application Routing and Peering Blue – Key Field (7) Red - Lookup Field (5) Black- Value Field (6)

Netflow Configuration Commands • ip flow-export version <version> [origin-as | peer-as | bgp-nexthop] – e. g. ip flow-export version 5 • ip flow-export destination <address> <port> – e. g. ip flow-export destination 10. 0. 0. 1 65001 • ip flow export source <interface> – default is interface with best route to collector. Recommendation: configure loopback interface. • ip flow-aggregation cache <name of aggregation scheme> – select the aggregation cache • ip flow-cache timeout inactive <seconds> – sets the seconds an inactive flow will remain in the cache before expiration. 15 seconds is default • ip flow-cache timeout active <mintues> – sets the minutes an active flow will remain in the cache bvefore expiration. 30 minutes is default • ip flow-cache entries <number> – sets the maximum number of flow entries in the cache. The default varies dependent on platform.

Netflow Show Commands • show ip cache [verbose] flow – shows Netflow statistics • show cache flow aggregation <name of aggregation scheme> – shows netflow statistics for the configured aggregation scheme • show ip flow export – shows export statistics • clear ip cache flow – clears netflow statistics • clear ip flow stats – clears export statistics

Show ip cache flow IP packet size distribution (2175 M total packets): 1 -32 64 96 128 160 192 224 256 288 320 352 384 416 448 480. 001. 440. 139. 014. 008. 000. 011. 000 512 544 576 1024 1536 2048 2560 3072 3584 4096 4608. 000. 002. 377. 000 IP Flow Switching Cache, 4456704 bytes 550 active, 64986 inactive, 509378135 added 3145787062 ager polls, 0 flow alloc failures Active flows timeout in 30 minutes Inactive flows timeout in 15 seconds Protocol Total Flows Packets Bytes Packets Active(Sec) Idle(Sec) -------Flows /Sec /Flow /Pkt /Sec /Flow TCP-WWW 10431912 2. 4 10 181 25. 7 7. 1 20. 4 TCP-SMTP 773843 0. 1 6 98 1. 1 8. 3 16. 7 ……. Total: 509377507 118. 5 4 567 506. 4 1. 7 15. 9 Src. If Te 7/3 Src. IPaddress 219. 245. 101. 77 84. 97. 234. 47 222. 81. 87. 163 Dst. IPaddress Pr 202. 205. 5. 3 tcp 202. 204. 192. 18 udp 202. 205. 3. 203 tcp Src. P 1444 7692 1172 Dst. P 1203 2881 Pkts 1 1

Show ip flow export Router> sh ip flow export Flow export v 5 is enabled for main cache Exporting flows to 192. 168. 1. 2 (2055) 192. 168. 2. 3 (2054) Exporting using source interface Loopback 0 Version 5 flow records, origin-as 998016649 flows exported in 33267252 udp datagrams 0 flows failed due to lack of export packet 0 export packets were sent up to process level 0 export packets were dropped due to no fib 0 export packets were dropped due to adjacency issues 0 export packets were dropped due to fragmentation failures 0 export packets were dropped due to encapsulation fixup failures 0 export packets were dropped enqueuing for the RP 0 export packets were dropped due to IPC rate limiting

Version 7 • Adds Net. Flow switching support for: ü Cisco Catalyst 5000 Series Switches with an RSM ü Cisco Catalyst 5000 Series Switches with an MSFC • Uses Multi. Layer Switching (MLS) or CEF with Cisco Catalyst 6000 Series Switches with SUP 2 • IP unicast only ü No multicast or IPX, even if MLS can do all three • MLS cache is the equivalent of the Net. Flow cache

Version 8 • • • Router-based aggregation Enables router to summarize Net. Flow data Reduces Net. Flow Export data volume Decreases Net. Flow Export bandwidth requirements Currently 11 aggregation schemes u Five original schemes u Six new schemes with the TOS byte field • Several aggregations can be enabled simultaneously

Version 9 l Fixed formats (versions 1, 5, 7, and 8) are not flexible and adaptable u Cisco needed to build a new version each time a customer wanted to export new fields l When new versions are created, partners need to reengineer to support the new export format Solution: Build a flexible and extensible export format!

Netflow v 9 Principles • • Version 9 is an export format Still a push model Sent the template regularly (configurable) Independent of the underlying protocol, it is ready for any reliable protocol (ie: TCP, SCTP) • Advantage: we can add new technologies and data types quickly • E. g. MPLS, IPv 6, BGP Next Hop, Multicast

Netflow V 9 Template • Net. Flow Version 9 Export format is template based. Version 9 record format consists of a packet header followed by at least one or more template or data Flow. Sets. A template Flow. Set (collection of one or more template) provides a description of the fields that will be present in future data Flow. Sets. Templates provide an extensible design to the record format, a feature that should allow future enhancements to Net. Flow services without requiring concurrent changes to the basic flow -record format. • template composed of type and length • flow records composed of template ID and value • sent the template regularly (configurable), because of UDP

Netflow Version 9 Scenario

Netflow v 9: Example for Template Definition

Netflow Version 9 Export Packet

Netflow v 9: Example for 1 Export Packet

Net. Flow v 9 Export Packet To support technologies such as MPLS or Multicast, this export format can be leveraged to easily insert new fields Header (version, # packets, sequence #, Source ID) Template Flow. Set Template Record Template ID #1 Template Record Template ID #2 (specific Field types and lengths) Flows from Interface A Data Flow. Set ID #1 Data Record (Field values) Flows from Interface B Data Flow. Set ID #2 Option Data Option Template Flow. Set ID Flow. Set Data Record Template ID (Field values) (specific Field types and lengths) Option Data Record (Field values) • Matching ID #s is the way to associate Template to the Data Records • The Header follows the same format as prior Net. Flow versions so Collectors will be backward compatible • Each Data Record represents one flow • If exported flows have the same fields then they can be contained in the same Template Record e. g. unicast traffic can be combined with multicast records • If exported flows have different fields then they can’t be contained in the same Template Record e. g. BGP next-hop can’t be combined with MPLS Aware Net. Flow records

Net. Flow v 9 Export test(config)# ip flow-export version ? 1 5 Configuring Version 9 9 test(config)# ip flow-export version 9 export. Export versions available for standard Net. Flow flows Configuring Version 9 export for an aggregation scheme test(config)# ip flow-aggregation cache as test(config-flow-cache)# enabled test(config-flow-cache)# export ? destination Specify the Destination IP address version configure aggregation cache export version test(config-flow-cache)# export version ? 8 Version 8 export format Export versions available for test(config-flow-cache)# export version 9 aggregated Net. Flow flows 9 Version 9 export format

IETF: IP Flow information Export(IPFIX) Working Group • IPFIX is an effort to: – Define the notion of a "standard IP flow" – Devise data encoding for IP flows – Consider the notion of IP flow information export based upon packet sampling – Identify and address any security privacy concerns affecting flow data – Specify the transport mapping for carrying IP flow information(IETF approved congestion-aware transport protocol) – Netflow version 9 has been selected as a basis for the IPFIX protocol

IETF: Packet Sampling WG(PSAMP) • PSAMP agreed to use IPFIX(Netflow version 9) for export • PSAMP is an effort to: – specify a set of selection operations by which packets are sampled – describe protocols by which information on sampled packets is reported to applicatons • http: //www. ietf. org/html. charters/psampcharter. html • Note: Netflow is already using some sampling mechanisms

Net. Flow Infrastructure

Net. Flow Uses Distribution • Attack Mitigation • User (IP) monitoring • Application monitoring • Billing • Chargeback • AS Peer Monitoring • Aggregation Schemes (v 8) • “show ip cache flow” command • Arbor Networks • Net. Flow MPLS Egress Accounting • BGP Next-hop (v 9) • Multicast Net. Flow (v 9) Core Distribution Access • Traffic Engineering • Traffic Analysis • Billing • Chargeback • AS Peer Monitoring • Attack Mitigation • User (IP) monitoring • Application monitoring • MPLS Aware Net. Flow (v 9) • BGP Next-hop (v 9) • Sampled Net. Flow • Net. Flow MPLS Egress Accounting • BGP Nexthop (v 9) • Multicast Net. Flow (v 9) • Aggregation Schemes (v 8) • “show ip cache flow” command • Arbor Networks Net. Flow Features Applications Network Layer Access

Netflow Collector(NFC) 5. 0

Netflow on the Network Analysis Module (NAM)

Netflow Partners

Billing l Flat-rate billing does not necessarily scale u. Competitive pricing models can be created with usagebased billing l Usage-based billing considerations u. Time of day u. Within or outside of the network u. Application u. Distance-based u. Quality of Service (Qo. S) / Class of Service (Co. S) u. Bandwidth usage u. Transit or peer u. Data transferred u. Traffic class

Tracking Users l Who are my top N talkers, and what percentage of traffic do they represent? l How many users are on the network at a given time? u When will upgrades affect the least number of users? l l How long do users spend connected to the network? Where Internet sites do they use? What is a typical pattern of usage between sites? Are users staying within an acceptable usage policy (AUP)? l Alarm DOS attacks like smurf, fraggle, and SYN flood u Will watch for these attack, regardless of source / destination

Principle Netflow Benefits Service Provider Enterprise • Traffic Engineering • Internet access monitoring (protocol distribution, where traffic is going/coming) • Accounting and billing • User Monitoring • Security Monitoring • Application Monitoring • Peering arrangements • Network Planning • Charge Back billing for departments • Security Monitoring

Net. Flow – Charge Back Billing Account per network (rather that per IP addresses) Example: charge the department for the cost of the Internet link Internet Finance HR R&D

Net. Flow – Peering Agreement Account per BGP AS, to Review Peering Agreements ISP

Net. Flow – Peering Agreement Public Routers 1, 2, 3 Month of September—Outbound Traffic 4% 2% 1% 1%1% 6% 1%1% 1% 1% 8% 8% 10% 32% 20%

MPLS Aware Net. Flow (v 9) Source and destination IP address Input and output sub-interfaces IP Fields Transport layer protocol Source and destination application port numbers 8 bit IP Type of Service (To. S) TCP Flags (accumulation from all packets in the flow) Up to three incoming MPLS labels with experimental (EXP) bits and end-of-stack (S) bit MPLS Fields Traditional Net. Flow Fields Position of each of the three labels Type of the top label IP address associated with the top label Number of packets Number of bytes (count either IP or MPLS header / payload) Time-stamps of first and last packets in the flow

MPLS Traditional Net. Flow for IP to MPLS traffic MPLS Aware Net. Flow (version 9) Egress MPLS Net. Flow Accounting for MPLS to IP traffic IP MPLS IP PE Traffic Flow Egress MPLS Net. Flow Accounting • IP information only • Ideal for billing • Current availability: Cisco IOS Software Releases 12. 0(10)ST and 12. 1(5)T MPLS Aware Net. Flow (version 9) • Exports up to three MPLS labels, and IP packet information • Ideal for Traffic Engineering • Will be available in Cisco IOS Software Releases 12. 0(24)S, 12. 2 S, and 12. 3

Autonomous System • Origin-AS Specifies that export statistics include the origin autonomous system (AS) for the source and destination • Peer-AS Specifies that export statistics include the peer AS for the source and destination 3600 -4(config)# ip flow-export version 5 ? origin-as record origin AS peer-as record peer AS <cr> 3600 -4(config)#

Autonomous System Net. Flow enabled AS 101 AS 102 AS 103 Configuring Peer-AS • Source AS = AS 103 • Destination AS = AS 105 AS 104 AS 105 Router(config)#ip flow-export version 5 peer-as AS 106

Autonomous System Net. Flow enabled AS 101 AS 102 AS 103 AS 104 AS 105 Router(config)#ip flow-export version 5 origin-as Configuring Origin-AS • Source AS = AS 101 • Destination AS = AS 106

BGP next-hop • Supported only in version 9 export • For traffic engineering/analysis and possible billing applications • Fields that are exported include all those found in version 5 export • Will be supported in Cisco IOS Software Releases 12. 0(26)S, 12. 2 S, and 12. 3

BGP next-hop

Netflow BGP next-hop

BGP next-hop Details • Supported only in version 9 export • For traffic engineering/analysis (traffic matrix) and possible billing applications. "What is the Next hop IP address of my BGP traffic? " • exported fields include all version 5 fields, including IP next hop • Adds 16 bytes to each Netflow record (goes from 64 bytes to 80 bytes), while CPU increase is negligible • Edge to Edge traffic matrix for engineering/analysis and possible billing applications • Supported in Cisco IOS Software releases 12. 0(26)S, 12. 2(18)S, and 12. 3(1)

BGP next-hop pamela(config)# ip flow-export version ? 1 5 Configuring Version 9 9 pamela(config)# ip flow-export version 9 export. Configuring Version 9 export with BGP next-hop pamela(config)# ip flow-export version 9 ? bgp-nexthop record BGP Next. Hop origin-as record origin AS peer-as record peer AS <cr> pamela(config)# ip flow-export version 9 bgp-nexthop

Multicast Net. Flow Three types of Net. Flow implementations for Multicast traffic: 1. Traditional Net. Flow 2. Multicast Net. Flow Ingress 3. Multicast Net. Flow Egress

Multicast – Traditional Net. Flow configuration (S, G) - (10. 0. 0. 2, 224. 10. 100) Interface Ethernet 0 Net. Flow Collector server ip route-cache flow 10. 0. 0. 2 Eth 0 ip flow-export version 9 ip flow-export destination 127. 0. 0. 1 9995 127. 0. 0. 1 Eth 3 Eth 2 Flow Record Created in Net. Flow Cache • • There is only one flow per Net. Flow configured input interface The 7 Key fields that define a unique flow are marked in red Destination interface is marked as “Null” Bytes and Packets are the incoming values

Multicast Net. Flow Ingress configuration Interface Ethernet 0 (S, G) - (10. 0. 0. 2, 224. 10. 100) 10. 0. 0. 2 ip multicast netflow ingress ip flow-export version 9 Eth 0 127. 0. 0. 1 Eth 3 ip flow-export destination 127. 0. 0. 1 9995 Eth 2 Flow Record Created in Net. Flow Cache • • Net. Flow Collector server There is only one flow per Net. Flow configured input interface The 7 Key fields that define a unique flow are marked in red Destination interface is marked as “Null” Bytes and Packets are the outgoing values

Multicast Net. Flow Egress configuration (S, G) - (10. 0. 0. 2, 224. 10. 100) Interface Ethernet 1 Net. Flow Collector server ip multicast netflow egress Interface Ethernet 2 10. 0. 0. 2 ip multicast netflow egress Eth 0 Interface Ethernet 3 ip multicast netflow egress 127. 0. 0. 1 Eth 3 ip flow-export version 9 ip flow-export destination 127. 0. 0. 1 9995 Eth 2 Flow Records Created in Net. Flow Cache • There is one flow per Multicast Net. Flow Egress configured output interface • One of the 7 Key fields that define a unique flow has changed from Source Interface to Destination Interface • Bytes and Packets are the outgoing values

Multicast Net. Flow – Summary l Supported via Net. Flow version 9 export format l Availability u. Cisco IOS Software Releases 12. 0(27)S, 12. 2 S, and 12. 3 u Not supported in 120000 l Performance: Ingress vs. Egress u. Multicast Net. Flow Ingress and traditional Net. Flow will have similar performance numbers u. Multicast Net. Flow Egress will have performance impact that is proportional to the number of interfaces on which it is enabled (include input interface) l Cisco Catalyst 6500/7600 Series Switches u. Do not currently support the tracking of multicast traffic via Net. Flow due to current ASIC limitation u. Will have this support in a future Supervisor

How to Identify a Security Attack? • Suddenly highly-increased overall traffic in the network • Higher CPU and memory utilization of network devices • Unexpectedly large amount of traffic generated by individual hosts • Increased number of accounting records generated • Multiple accounting records with abnormal content, like one packet per flow record (e. g. TCP SYN flood) • A changed mix of traffic applications, e. g. a sudden increase of "unknown" applications • An increase of certain traffic types and messages, e. g. TCP resets or ICMP messages • An increasing number of ACL violations

What Does a DOS Attack Look Like?

Net. Flow – Mitigating Attacks 1. Cost Saver • • “sh ip cache flow” command to find top volume flows Identify source of attack Write access-list to block Monitor via “show ip cache flow” & “Null” entry in Dest. If field to show that it is blocked • Prefix-port aggregation can be configured, while “sh ip cache flow aggregation prefix-port” is used 2. Most Effective • Arbor Networks leverages Net. Flow to provide a quicker response and more sophisticated solution

Security Analysis: Best Practices

Quality of Service Example To. S bits Precedence bits DS 5 DS 4 DS 3 DS 2 DS 1 DS 0 ECN 128 64 32 16 8 4 2 1 Diff. Serv field AKA IP DSCP markings Early Congestion Notification (ECN) bits

Quality of Service Example

Tracking TOS with Net. Flow Hex 7200 -3 -netflow# show ip cache verbose flow Src. If Src. IPaddress Dst. If Port Msk AS SR 6/0 210. 2 PO 1/0 0000 /0 0 Dst. IPaddress Next. Hop 200. 2 0. 0 Pr TOS Flgs Pkts B/Pk Active FF 00 10 21 K 1496 665. 4 06 C 0 00 21 K 1496 666. 0 7200 -3 -netflow# show ip cache verbose flow Src. If Src. IPaddress Dst. If Port Msk AS Et 1/1 52. 52. 52. 1 Fd 4/0 0000 /8 50 0000 /8 40 Et 1/2 10. 1. 3. 2 Fd 4/0 0000 /0 0 0000 /8 40 Dst. IPaddress Next. Hop 42. 42. 42. 1 202. 120. 130. 2 Pr TOS Flgs Pkts B/Pk Active 01 55 10 3748 28 17. 8 01 CC 10 3568 28 17. 8 01 C 0 10 1124 28 17. 8 Decimal Binary 55 85 0101 of transport protocol ECN-capable Precedence 2 - Immediate (Class 2), Delay - low, Reliability - high, Endpoints C 0 1100 0000 Precedence 6 - Internetwork Control (Routing Protocols) 1100 Precedence 6 - Internetwork Control (Routing Protocols), Throughput - high, 192 CC 204 Reliability - high

Sampled Net. Flow l. Deterministic u. Original type u. Cisco 12000 Series Internet Routers u. Cisco Catalyst 6500 Series Switches – Release 12. 1(13)E l. Random (recommended per statistical principles) u. Cisco IOS Software Releases 12. 0(26)S, 12. 2 S, and 12. 3 u. Cisco 2500, 2600, 3600, 7200, and 7500 Series Routers u. Cisco 12000 Series Internet Routers l. Time-based u. Cisco Catalyst 6500 Series Switches – Release 12. 1(13)E l. Trajectory (Hash-based) uin development

Sampling configuration • GSR 12 xxx (IOS Version: 12. 0(31)S 2: R 1(config)# ip flow-sampling-mode packet-interval 256 R 1(config-if)# ip route-cache flow sampled input R 1(config-if)# ip route-cache flow sampled output bj 2 -bgw(config)#ip flow-sampling-mode packet-interval ? <10 -16382> Specify the packet interval at which to sample • 7609: (12. 2(18)SXD 6) R 1(config)# mls flow ip source R 1(config)# mls nde sender version 5 R 1(config)# mls sampling time-based 64 R 1(config-if)# ip route-cache flow R 1(config-if)# mls netflow sampling // 64: 1

Cisco Catalyst 6500 and 7600 Series Switches • Export is centrally via the supervisor and MSFC, each line card has its own hardware Net. Flow cache and forwarding table, i. e. distributed platform

Cisco 12000 Series Internet Routers – Net. Flow • Engine 0 – software support • Engine 1 – software support • Engine 2 – supported in ASICs, but lower priority so beware if running many other features • Engine 3 – version 5 support in software, version 8 support in ASIC • Engine 4 – not supported • Engine 4+ – supported in ASICs

Cisco 12000 Series Internet Routers Sampled Net. Flow Engine Full Net. Flow Sampled Net. Flow 0 1 2 3 4 4+ Supported Not supported

Scaling - Memory Utilization

Scaling - Sample Traffic Deterministic vs. Random Sampling

Sampled Netflow Details • Deterministic – Cisco C 6500/7600 Series switches(12. 1(13)E) – Cisco 12000 series internet routers (12. 0(11)S and 12. 0(14)ST) • Random (select packet to export per statistical principles) – Cisco IOS Software Releases 12. 0(26)S, 12. 2 S(18), and 12. 3(1)T – Cisco 800, 1700, 1800, 2600, 2800, 3600, 3700, 3800, 7200, and 7500 series routers • Time-based – Cisco C 6500/7600 series Random and Time based sampling 12. 1(13)E

Sampled Netflow CPU Reduction

Netflow Multiple Export Destinations

Performance Testing Conclusions • Additional CPU utilization Number of Active Flows Additional CPU Utilization 10, 000 <4% 45, 000 <12% 65, 000 <16% • Net. Flow Data Export (single/dual) No significant impact • Net. Flow v 5 versus v 8: little or not impact • Net. Flow Feature Acceleration: >200 lines of ACLs and/or Policy Based-Routing (PBR) • Net. Flow versus Sampled Net. Flow on the Cisco 12000 Series Internet Routers 23% versus 3% (65, 000 flows, 1: 100)

Performance Testing Net. Flow Version 9 • Similar CPU and throughput numbers result from configuration of both Net. Flow version 5 and 9 • No change in Net. Flow performance after the addition of version 9 Cisco IOS Software Releases 12. 0(24)S, 12. 2 S, and 12. 3 • CPU is slightly higher immediately following initial boot up or configuration Caused by sending Template Flowsets to Collector

Reducing Performance Impact Reduce CPU and memory impact on the router, collector, or network: • • • Aging timers (router) Sampled Net. Flow (router) Enable Net. Flow Feature Acceleration (router) Flow Masks (only Cat 6000/7600) Enable on specific sub-interface (upcoming router feature) Aggregation schemes (v 8 on router or on collector) Filters (router or collector) Data Compression (collector) Increase collection bucket sizes (collector) Collector and router can be placed on the same LAN segment (network)

Netflow Deployment: Rules of Thumb

Netflow Deployment: Considerations

Cisco Netflow MIB

Netflow MIB applications • Netflow Configuration • Checking Netflow Configuration • Monitoring and security – export statistics – protocol statistics – top flows information (top talkers)

Netflow Mib Overview • Defined groups of objects 1. cnf. Cache. Info • A group of objects related to cache information and configuration stored per cache configuration. 2. cnf. Export. Info • A group of objects related to Export configuration and information. 4. cnf. Export. Statistics • Provides export statistics. 5. cnf. Protocol. Statistics • Provides a summary of Net. Flow cache statistics per protocol and port. 6. cnf. Export. Template • Provides Template based Version 9 flow export information and statistic. 7. cnf. Top. Flows • Provides top Netflows.

Netflow MIB Monitoring

Egress Netflow Accounting

Netflow and IPv 6 • • • Collects IPv 6 flow records Based on Netflow Version 9 Support or both ingress and egress traffic "Full Net. Flow" i. e. non-sampled Data export is still IPv 4 Available in release 12. 3(7)T

Netflow Summary • Netflow is a mature Cisco IOS feature (in Cisco IOS since 1996) • Netflow provides input for Accounting, Performance, Fault, Security, and Billing Applications • Cisco has IETF and industry leadership • Netflow v 9 eases the exporting of additional fields • A lot of new features have been added

SFlow • s. Flow® is an industry standard technology for monitoring high speed switched networks, Juniper’s devices support it. • • similar to netflow Net. Stream from Huawei Company • SFlow Packet: ü ü ü ü ü Packet header (eg MAC, IPv 4, IPv 6, IPX, Apple. Talk, TCP, UDP, ICMP) Sample process parameters (rate, pool etc. ) Input/output ports Priority (802. 1 p and TOS) VLAN (802. 1 Q) Source/destination prefix Next hop address Source AS, Source Peer AS Destination AS Path Communities, local preference ü User IDs (TACACS/RADIUS) for source/destination ü URL associated with source/destination ü Interface statistics (RFC 1573, RFC 2233, and RFC 2358)

Tools for Netflow • Cisco NFC • Arbor Peakflow • Flow tools • Ntop – http: //ww. ntop. org • Etc.

Flow-tools • Flow-tools is library and a collection of programs used to collect, send, process, and generate reports from Net. Flow data. • Can be used together on a single server or distributed to multiple servers for large deployments. • The flow-tools library provides an API for development of custom applications for Net. Flow export versions 1, 5, 6 and the 14 currently defined version 8 subversions. • Version 9 is not supported now

Flow-tools utilities • • flow-capture - Collect, compress, store, and manage disk space for exported flows from a router. flow-cat - Concatenate flow files. Typically flow files will contain a small window of 5 or 15 minutes of exports. Flow-cat can be used to append files for generating reports that span longer time periods. flow-fanout - Replicate Net. Flow datagrams to unicast or multicast destinations. Flow-fanout is used to facilitate multiple collectors attached to a single router. flow-report - Generate reports for Net. Flow data sets. Reports include source/destination IP pairs, source/destination AS, and top talkers. Over 50 reports are currently supported. flow-tag - Tag flows based on IP address or AS #. Flow-tag is used to group flows by customer network. The tags can later be used with flow-fanout or flow-report to generate customer based traffic reports. flow-filter - Filter flows based on any of the export fields. Flow-filter is used in-line with other programs to generate reports based on flows matching filter expressions. flow-import - Import data from ASCII or cflowd format. flow-export - Export data to ASCII or cflowd format.

Flow-tools utilities( Cont. ) • flow-send - Send data over the network using the Net. Flow protocol. • flow-receive - Receive exports using the Net. Flow protocol without storing to disk like flow-capture. • flow-gen - Generate test data. • flow-dscan - Simple tool for detecting some types of network scanning and Denial of Service attacks. • flow-merge - Merge flow files in chronoligical order. • flow-xlate - Perform translations on some flow fields. • flow-expire - Expire flows using the same policy of flowcapture. • flow-header - Display meta information in flow file. • flow-split - Split flow files into smaller files based on size, time, or tags.

Configuration in Cisco Router R 1(config)# ip flow-export source Loopback 0 R 1(config)# ip flow-export version 5 origin-as R 1(config)# ip flow-export destination 202. 112. xx 9800 R 1(config-if)# ip route-cache flow

flow-capture • Flow-tools most useful and important command • flow-capture -w /flows/dat -m 255. 248. 0 -E 5 G 0/10. 0. 0. 1/9800 – Receive flows from the exporter at 10. 0. 0. 1 port 9800. Maintain 5 Gigabytes of flow files in /flows/dat. Mask the source and destination IP addresses contained in the flow exports with 255. 248. 0. • flow-capture -w /flows/dat 0/0/9800 -S 5 – Receive flows from any exporter on port 9800. Do not perform any flow file space management. Store the exports in /flows/dat. Emit a stat log message every 5 minutes.

Flow-cat

Flow-print Free. BSD 1# flow-print < ft-v 01. 2006 -09 -02. 134114+0800 src. IP 202. 204. 79. 253 dst. IP prot 202. 204. 239. 227 6 202. 204. 239. 229 6 202. 204. 239. 240 6 202. 204. 239. 228 6 202. 204. 239. 233 6 202. 204. 239. 231 6 s. Port d. Port octets 4414 1433 48 4450 1433 96 4535 1433 48 4443 1433 48 4472 1433 96 4461 1433 48 pkts 1 2 1

Flow-stat

Flow-stat exam. 1 % flow-cat -p /flows/dat | flow-stat IP packet size distribution: 1 -32 64 96 128 160 192 224 256 288 320 352 384 416 448 480. 000. 906. 029. 004. 002. 009. 001. 004. 027. 004. 000 512 544 576 1024 1536 2048 2560 3072 3584 4096 4608. 000. 001. 012. 000 Packets per flow distribution: 1 2 4 8 12 16 20 24 28 32 36 40 44 48 52. 812. 157. 010. 013. 006. 001. 000. 000 60 100 200 300 400 500 600 700 800 900 >900. 001. 000 Octets per flow distribution: 32 64 128 256 512 1280 2048 2816 3584 4352 5120 5888 6656 7424 8192. 000. 754. 183. 009. 012. 015. 014. 008. 004. 002. 000 8960 9728 10496 11264 12032 12800 13568 14336 15104 15872 >15872. 000. 001. 000. 001 Flow time distribution: 10 50 100 200 500 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000. 812. 000. 001. 131. 015. 001. 004. 002. 001 12000 14000 16000 18000 20000 22000 24000 26000 28000 30000 >30000. 001. 002. 001. 000. 017

formats

Flow-stat exam. 2 • flow-cat -p /flows/dat | flow-stat -f 10 -S 4 – Provide a report on top source/destination IP pairs sorted by octets # Fields: Total # Symbols: Disabled # Sorting: Descending Field 4 # Name: Source/Destination IP # # src IPaddr dst IPaddr flows # 202. 204. 192. 1 10. 20. 0. 12 1 202. 204. 192. 1 10. 20. 0. 8 3 202. 204. 192. 1 10. 20. 0. 9 2 202. 204. 193. 1 64. 84. 7. 4 1 202. 204. 148 221. 137. 69. 66 3 216. 186. 143. 246 202. 204. 227. 118 1 202. 204. 79. 253 202. 204. 239. 233 1 octets packets 3720 3128 3269 390 144 96 12 11 11 3 3 3 2