Contents
How to use HSRP to provide redundancy in a multihomed BGP?
In this diagram, Router 1 (R1) and Router 2 (R2) are in AS 100, which has external BGP (eBGP) peering with ISP-A (AS 300) and ISP-B (AS 400) respectively. Router 6 (R6) is a part of AS 600, which has eBGP peering with ISP-A and ISP-B. R1. R2 has iBGP peering, which is necessary to ensure optimal routing.
How does GLBP prevent single point of failure?
GLBP (Gateway Load Balancing Protocol) prevents a single point of failure, like HSRP and VRRP, but also allows load-sharing among a group of redundant routers. Multiple first-hop routers on the LAN form a group to offer a single virtual router, also sharing the IP packet forwarding load.
How to see the active HSRP router on R1?
Issue the show standby command in order to see the active HSRP router when the interface s0 on R1 is up: The show standby command shows R1 as the active HSRP router because of the higher priority of 105. Since R1 is the active router, R1 owns the standby IP address 192.168.21.10.
How does HSRP and VRRP work for multiple routers?
HSRP and VRRP also allow multiple routers to form a virtual router group with a virtual IP address. But only one member of the group is elected as the active router that forwards packets sent to the virtual IP address for the group. The other routers in the group stay idle until the active router fails.
Which is the standby IP address for HSRP R1?
Since R1 is the active router, R1 owns the standby IP address 192.168.21.10. All IP traffic from the host configured with the default gateway to 192.168.21.10 routes through R1. If you bring the s0 interface on Router R1 down, the HSRP active router changes since HSRP on R1 is configured with the standby track serial 0 command.
What happens to HSRP when serial 0 goes down?
If you bring the s0 interface on Router R1 down, the HSRP active router changes since HSRP on R1 is configured with the standby track serial 0 command. When the Serial 0 interface protocol goes down, HSRP reduces the priority of R1 by 10 (default) to 95.
When does connectivity break between R1 and ISP-a?
When connectivity breaks between R1 and ISP-A, R6 must choose the alternate path through ISP-B to reach network 192.168.21.0/24 in AS 100: This is the BGP table in R6 for the network 192.168.21.0/24: