BGP route selection from LAN to WAN

[Goutam Biswas]

Hi,

I am going to implement a multihome internet connection to two different ISP. Before implementing in real network, I have prepared the same in GNS3 and testing. Subnet 10.x.5.0/24 should take R1 to outside from LAN and 10.x.6.0/24 should take R2 to outside from LAN.

Below is my configuration;

• HSRP between R1 and R2 towards LAN. R1 is the primary HSRP device.
• R6 is the host (example) and subnet .5.0/24 and .6.0/24 are connected to R6.
• R6 is sending a default route to HSRP VIP.
• R1 is advertising subnet 10.x.5.0/24 and R2 is advertising subnet 10.x.6.0/24
• iBGP is configured between R1 and R2

From Internet to LAN:

From router 5 (exam.: Internet) traffic is divided in to two routers. traffic for 10.x.5.0/24 coming to R1 and traffic for 10.x.6.0/24 coming to R2. This is absolutely fine. What i expected.

From LAN to Internet:

I need traffic from 10.x.5.0/24 should take R1 to go to internet (outside) and from 10.x.6.0/24 should take R2 to go to Inernet (outside).

I have tried with higher Local Preference on each router but is not working. All traffic from R6 (i.e. LAN) to outside is taking only R1 to go outisde.

Could any one can help on how I can share traffic for 10.x.5.0/24 & 10.x.6.0/24 divided in two Routers from LAN.

Diagram is attached.

[Leo Laohoo]

Duplicate post.

Go HERE.

[Goutam Biswas]

Hi,

Same post i have done in LAN, Switching and Routing.  But later i thought question should be in WAN, Switching and Routing.  So i have posted here and deleted from there.

[Akash Agrawal]

As answered in other post, hosts belong to LAN2 (subnet 10.x.6.0/24) can have default gateway set to R2 (R2 could be HSRP active node) now R2 will have route from eBGP (AS300) as well ibgp session (from R1). We can tweak BGP attribute to prefer eBGP session. One good option is to set weight as we want to prefer AS300 routes locally to the router and not on R1. Similarly on R1 put weight for AS200 routes.

Regards,

Akash

[Goutam Biswas]

Hi,

to make R2 as HSRP active node, then I need to configure another hsrp instance. even i have tried with your later part which is configuring weight.

I have set weight from R2 to R1 (iBGP) 1000 and R2 to R4 (eBGP) 2000 same on R1.  in this case all traffic from LAN (R6) is taking R2 to go out, did not get why.

if possible can you explain little bit more.

[Akash Agrawal]

Hi,

How R6 traffic comes to R1 or R2? does it have all routes or it having default route to the VIP of hsrp. If it is default route then any changes with BGP on R1 and R2 should not affected lan traffic chossing R1 or R2 as gateway. After this setting weight on R2 should not change routing on R1. R1 should still prefer ebgp routes.

[Goutam Biswas]

Hi,

yes R6 is sending default route to VIP ip address of R1 and R2. How do I change default route because those two subnets are belong to R6 only so I cannot change to static route with source IP address.