Virtual Router Redundancy Protocol VRRP Speaker LiWen Chen

Virtual Router Redundancy Protocol (VRRP) Speaker: Li-Wen Chen Date: 2010 -08 -12 1

Outline l Introduction l Glossary l Relevant fields in the VRRP header l Sample Configuration l Elections of master routers l Reference 2

Introduction l Virtual Router Redundancy Protocol (VRRP) [RFC 3768] ¡ ¡ l is designed to eliminate the single point of failure inherent in the static default routed environment. specifies an election protocol that dynamically assigns responsibility for a virtual router to one of the VRRP routers on a LAN. VRRP provides a function similar to ¡ ¡ a Cisco Systems, Inc. proprietary protocol named Hot Standby Router Protocol (HSRP). a Digital Equipment Corporation, Inc. proprietary protocol named IP Standby Protocol (IPSTB). 3

Glossary l a virtual router ¡ an abstract representation of master and backup physical routers acting as a group consists of a Virtual Router Identifier (VRID) and a set of associated IP address(es) across a common LAN. l master router ¡ ¡ l performs packet forwarding for local hosts answers ARP requests for these IP address(es) associated with a virtual router only one master router doing the actual routing backup routers ¡ “back up” in case the master router fails 4

Relevant fields in the VRRP header 5

Relevant fields in the VRRP header l Priority ¡ A value between 0 -255. ¡ 0: indicate the current Master has stopped participating in VRRP ¡ 255: for the VRRP router that owns the IP address(es) associated with the virtual router l Note that if the IP address owner is available, then it will always become the Master. 1 -254: for the VRRP routers backing up a virtual router l VRID (Virtual Router IDentifier) ¡ different for each virtual router in the network ¡ used by only one physical router at a time ¡ in the range 1 -255 ¡ 6

l MAC address: 00 -00 -5 E-00 -01 -[VRID] ¡ This address is used by only one physical router at a time, and it will reply with this MAC address when an ARP request is sent for the virtual router's IP address. l Physical routers within the virtual router must communicate within themselves using packets with multicast IP address 224. 0. 0. 18 ¡ and IP protocol number 112. ¡ 7

v. IP: 10. 0. 0. 10 v. MAC: 0000. 5 e 00. 0100 virtual router master backup VRRP physical router IP: 10. 0. 0. 253 MAC: 0000. 0 C 78. 9 abc physical router IP: 10. 0. 0. 254 MAC: 0000. 0 c 12. 3456 8

Sample Configuration 1 9

Sample Configuration 2 10

Elections of master routers l Master router sends an advertisement to the backups. ¡ Advertisement intervals can be set by the user; the VRRP default is 1 second. If the advertisements suddenly stop, the backups set interval timers, typically for three times the advertisement frequency. l If no further advertisements appear, the backups assume the master is down and the failover routine is activated. l ¡ From that point, the election of the next-in-line master typically takes less than a second. 11

Reference l http: //tools. ietf. org/html/rfc 3768 l http: //en. wikipedia. org/wiki/Virtual_Router_ Redundancy_Protocol l http: //tavi. debian. org. tw/index. php? page= VRRP l http: //fantasymew. pixnet. net/blog/post/239 39888 12