Sunday, 11 March 2012

Cisco IS-IS and OSPF prefix prioritisation

This post explains how prefix prioritisation can be configured in both IS-IS and OSPF to gain faster convergence.  This is particularly useful for MPLS or financial SSM multicast environments where we can easily distinguish the routes that should receive priority.

Saturday, 3 March 2012

Cisco Carrier Delay

Here are some quick tips on fast convergence on Cisco using Carrier Delay.

The quickest way to converge a network is when the router notices an interface go down, this is controlled by the carrier delay setting.  On WAN circuits, or where switches are between two routers, we may need to rely on our IGP/BGP/BFD timers, so this is not a replacement for tuning those parameters too.

Friday, 2 March 2012

F5 Big-IP Auto Last Hop

Here is a quick note on a not very well understood Big-IP feature

Auto Last Hop maintains a connection table recording the interface and MAC address of the upstream device which sent the flow to the Big-IP and sends reply packets to this interface/MAC address.   This feature can also be called “reverse persistence”.