Need Suggestion on Traffic Routing Options

[cumminswan]

Hi,

Please share how we can do routing on below scenario

We have two Routers R1 & R2 which are connected Active standby Scenarios where R1 is acting as Active & R2 as a Standby devices from BGP perspectives & both routers are connected to downward switching S1, S2 in below fashion.

We are using IBGP from R1-----> S1, S2 , R2 ----> S1,S2, R1---->R2

Now user requirement is to route only two VLAN traffic (suppose 201, 202) through backup router then how we can achieve it ? Keeping other traffic intact

[Georg Pauwen]

Hello,

you cannot selectively run traffic through an HSRP standby router. What are you trying to accomplish ?

[paul driver]

Hello

You can use the bgp path attributes (PA's) (such as local preference,as-path,metric cost communitys etc.) or Policy Based Routing (PBR) -However these options have differing results - but either one you choose you may also need to take into account asymmetric routing regards the return traffic

If you use Policy Based Routing (PBR) you can specify certain internal users/subnets to be policy routed via the 2nd bgp path but here you dont really have any control on the return traffic.

Using BGP cost communities you can specify on certain received routes a bgp community cost to either the least/best preffered bgp peer/path you wish for internal users to take.

Using BGP local preference for egress traffic you can specify on certain received routes you wish for internal users to take the 2nd path for.

Using BGP  as-path prepending for ingress traffic you can specify certain internal prefixes that you wish to be advertised with a longer as-path sequence towards the least preferred isp, The isp in turn will see these routes with a longer as-apath and so will take the shorter path back towards your rts which will be rtr2.