Thursday, August 18, 2011

Configuring BGP - Route Reflectors

To route reflect, or not to route reflect, that is the question. If a full iBGP mesh is required then consider Route Reflectors. If you had to iBGP full mesh 10 sites you would need 45 iBGP connections (10*(9)/2 or n * (n-1)/2 where n is the # of sites) = NIGHTMARE!!! In this blogtorial I will show you how to deploy a route reflector and drastically reduce the number of connections needed to achieve the same results as a full iBGP mesh design. 

Consider the simple topology and let's get started. 

Relevant configurations are posted below.

Tuesday, August 16, 2011

Configuring FHRP - IRDP

The less known, the unpopular, the quiet and the secretive protocol of First Hop Redundancy Protocol (FHRP) is ... dun dun dun .. IRDP (ICMP Router Discovery Protocol). In this blogtorial we will configure IRDP which uses 'ICMP' to send the default gateway information to hosts. This will be a short and simple blogtorial so consider the topology below and let's get started.

  • Configure R1 and R2 to with IRDP
  • R1 should be the primary default gateway and R2 should be the backup default gateway
  • R2 should take over when R1 goes down
Relevant configurations are posted below. 

Configuring FHRP - VRRP

Both FHRPs (HSRP & GLBP) are Cisco proprietary so what do you when you have to support a Cisco and a non-Cisco device in a redundant setup? Well you turn to the industry standard Virtual Router Redundancy Protocol (VRRP) RFC 2338. One of the biggest advantages of using VRRP is that you do not need an additional IP for the "Virtual IP". It can be the IP of the actual interface. For example in both HSRP and GLBP blogtorial you can see how my virtual IP was set to, however on this blogtorial notice that my virtual IP is the same as R1's interface IP ( 

Consider the topology and let's get started. 

  • Configure R1 and R2 with VRRP and authentication
  • R1 should be the master router and R2 should be the backup router. 
Relevant configurations are posted below. 

Monday, August 15, 2011

Configuring FHRP - GLBP

In my previous blogtorial we saw how we can configure HSRP. One downfall for using HSRP is that you can only use one router at a time. What if you wanted to use both R1 and R4 for load-balancing and failover? This is where Gateway Load Balancing Protocol comes in. Note that GLBP is Cisco proprietary. 

Consider the simple topology below. 

  • Configure R1 and R4 in a GLBP group with authentication
  • Configure R1 to be Active Virtual Gateway (AVG) and R4 to be Active Virtual Forwarder (AVF)
Relevant configurations are posted below. 

Configuring FHRP - HSRP

In any network, redundancy and high availability should be a top priority especially when it involves mission critical applications. In this blogtorial I am going to walk you through how to configure Hot-Standby Routing Protocol aka. HSRP. HSRP is a one of many First Hop Redundancy Protocol (FHRP). Note that HSRP is Cisco proprietary.

Consider the topology below and let's get started.

  • Configure HSRP on R1 and R2 with authentication.
  • Enable failover in less than a second. 
  • R1 should be the active router and R2 should be on standby
  • If R1 goes offline, then R2 should take over and when R1 comes back online then R1 should take over. 
Relevant configurations are posted below so let's proceed.