BGP/old setup

The pmtpa cluster has L3 failover using two separate core routers, and 2 BGP links to upstream.

Diagram

HSRP

In order to have first hop failover, i.e. failover of the default gateway of all hosts in the network, HSRP has been implemented on VLAN 1 and 2 on both routers, csw1-pmtpa and csw2-pmtpa. Both routers share a "virtual IP", the gateway IP that has been configured on all hosts. One of both routers is active for the IP, the other is in standby, taking over within seconds when the active router fails. Besides the virtual IP, each router has its own unique IP in the respective subnet.

VLAN 1 makes use of HSRP group 1, VLAN 2 uses HSRP group 2. In both cases csw1-pmtpa has the highest priority and is therefore the default router, but preemption is disabled, so the default router won't force itself to be the active router once it comes back up.

Configuration csw1-pmtpa

The relevant configuration bits are:

interface Vlan1
  description Public VLAN / interface
  ip address 207.142.131.240 255.255.255.192
  standby 1 ip 207.142.131.193
  standby 1 priority 150
end

interface Vlan2
  description Private VLAN: Apache
  ip address 10.0.0.201 255.255.0.0
  standby 2 ip 10.0.0.200
  standby 2 priority 150
end

Configuration csw4-pmtpa

The relevant configuration bits are:

interface Vlan1
  description Public VLAN
  ip address 207.142.131.244 255.255.255.192
  standby 1 ip 207.142.131.193
end

interface Vlan2
  description Private VLAN
  ip address 10.0.0.202 255.255.0.0
  standby 2 ip 10.0.0.200
end 

External links

• Configuring HSRP on Cisco 3560