Bidirectional Forwarding Detection Anilkumar Dantu CCIE 22536 HTTS

Bidirectional Forwarding Detection • Anilkumar Dantu CCIE (22536) HTTS, Cisco Systems Saurabh Shrivastava CCIE (40947) HTTS, Cisco Systems

Ø Ø Ø BFD Protocol Overview How BFD works BFD configuration in IOS BFD configuration in XR BFD configuration between IOS & XR node BFD Troubleshooting © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 2

Ø Networks carrying real time traffic need speedy network convergence. Ø Failure detection time consumes most of Network convergence budget. Ø Traditionally failure detection. a) Hello message timeouts of Routing protocols. b) Transmission technology capability to detect failure. Ø Bidirectional Forwarding detection : - Lightweight hello protocol (RFC 5880) - Independent of routing protocol hellos - Helps failure detection (milliseconds) © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 3

Ø ON Distributed Routing Platforms a) BFD packets processed at Line card. b) Hello packets of Routing protocol processed at RP CPU. Ø BFD also provides failure detection on virtual circuits, MPLS LSP …. © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 4

Ø BFD Modes of Operation a) Asynchronous mode b) Demand mode Ø BFD Configuration : Two Step Process Step 1: Enable BFD on Interface Step 2: Configure routing protocols/Clients to use BFD Ø Interested clients (OSPF, BGP, HSRP, MPLS LSP, etc. ) registers with BFD and is notified as soon as BFD detects a neighbor loss. © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 5

Ø BFD session 3 -way handshake and town down process 1 Routing protocol discovers neighbor and registers neighbor with BFD as a client 2 BFD control packets act as keepalive 3 BFD session failure notifies registered routing protocol clients to tear down their session Ø One BFD session for multiple client protocols or applications. © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 6

ØIOS BFD configuration - BFD Interface level configuration - BFD Routing Protocol Level configuration ØIOS BFD verification command: - show BFD neighbor detail Note: Verification commands should be run by attaching to LC for proper statistics. © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 7

Ø XR BFD configuration - No Interface level configuration - Routing Protocol Level configuration Ø XR verification command: - use location - show BFD session [Location xx] - show BFD session detail [Location xx] © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 8

Ø IOS BFD configuration - Interface Level configuration - Routing Protocol Level configuration ØXR BFD configuration - No Interface level configuration - Routing Protocol Level configuration Ø IOS verification command : - Attach to LC - show BFD neighbor [detail] Ø XR verification command: - use location - show BFD session [Location xx] © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 9

ØTypical BFD issues - BFD session down - BFD/Client session is flapping Ø IOS/XR Troubleshooting : - Verify configuration on both ends - Show bfd neighbor /session [detail] at LC - BFD debug command : debug BFD event/packet -Show tech-support routing bfd © 2010 Cisco and/or its affiliates. All rights reserved. (XR node). Cisco Confidential 10

Thank you.