BGP and EIGRP

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Nov 12th, 2008
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guys i have two question and if someone can please explain me......till now i thought that we only use next hop self command in ibgp......today i was doing something and i have seen this command for EBGP??? is it possible....as it was v strange???? can someone explain.....secondly in eigrp we use offset list...if we use it with 0 wht will happen......do we ahve to config access-list for every offset list??? i m bit confuse...thanks guys

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Giuseppe Larosa Wed, 11/12/2008 - 23:11
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Hello Khan,

there is an EIGRP interface command that allows to keep the original next hop in routes: it is used together with

int tunnel 100

no ip split-horizon eigrp as-number

no ip next-hop-self eigrp autonomous-system-number


typical usage is in DMVPN using EIGRP on the multipoint GRE virtual flat network on the hub(s) routers.

Without the no ip next-hop-self eigrp autonomous-system-number spoke routers see routes of other spokes with a next-hop = hub router address and this doesn't allow the setup of a dynamic spoke to spoke ipsec tunnel.

Disabling split-horizon is needed to make the hub router able to send updates out the same interface it has learned them.(distance vector aspect of EIGRP)


b) offset-list

if you provide an offset of 0 you are doing nothing.

An offset-list uses an acl to specify over what routes (if present) to apply its metric change action

the acl is a required parameter note the curly brackets { this means mandatory parameter


offset-list {access-list-number | access-list-name} {in | out} offset [interface-type interface-number]


[optional parameter] is to specify an interface


see


http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_eig2.html#wp1012264


Hope to help

Giuseppe


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