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bgp guru

Have a customer that has two isps at different locations. They run ebgp to carriers and ibgp to an inside switch. The problem is this using the same internal AS number they have connected switch site A to switch site B and these learn each others routed through a redistribute connected. However, they did not mesh the ibgp so the routers at each site only know the subnets that were redistribute connected to the directly connected switch. Short of meshing it together is there a way to have the routers learn the routes or would I have to create network statements and filter lists to make it happen

3 REPLIES
Hall of Fame Super Silver

Re: bgp guru

Hello Bill,

neighbor xxx allow-as-in 1 to accept the subnets of the other site from the eBGP session.

if you use prepending you will need to use a greater value

Hope to help

Giuseppe

New Member

Re: bgp guru

Giuseppe,

Thanks, lets make sure I have this straight

Site A

router A AS 1 to provider AS 2 to inside switch A

inside switch A AS 2 to site B switch B

switch A sees the routes generated from distribute connected from Switch B

Router A sees redistribute connected routes from switch A but does not see routes from switch B. Where exactly would I put this command. Remember Router A is not receiving any routes except default 0 from provider. Does that make sense?

Hall of Fame Super Silver

Re: bgp guru

Hello Bill,

my suggestion was under the hyphotesis that you were going to learn site B routes from the eBGP session with the provider.

If you receive only a default route from the provider my suggestion is out of context.

Probably you can already reach the remote site public ip addresses from siteA without any additional configuration.

If you mean to join two infrastructure IP addressing including private addressing this is a different issue.

You could try to build a logical link between the two sites using a GRE tunnel and running your IGP or a dedicated IGP over it.

In this case you could reach private ip addresses on site B from site A.

Other possible solutions are available: for example instead of the tunnel you can purchase an EoMPLS L2 point-to-point service from an MPLS Service Provider to avoid any additional overhead caused by tunnel encapsulation.

Prices should be interesting.

Hope to help

Giuseppe

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