Re: BGP TTL

Hi kid,

regardsless of data plane or control pale TTL value is reduced .

 The moment any interface receives a packet the TTL will be reduced by 1 .

On Fri, Oct 21, 2011 at 2:25 PM, CCIE KID <eliteccie_at_gmail.com> wrote:

> Hi fellas,
>
> I am working on BGP and i find in sh ip bgp neighbor command, the incoming
> TTL and the outgoing TTL . I understood the outgoing TTL is the one when
> the
> control plane packets are generated , the TTL in the IP Header will be 255.
> I find the incoming TTL to 0 . Can anyone explain me what is actually meant
> by incoming TTL.

> My understanding is the incoming TTL is the when the
> neighbor send u any BGP Control plane packet, the local router is expecting
> this TTL value in the IP HEader. Am i right ?
> So the incoming TTL valus is 0 in my case..
>

regardless of any operation , the TTL value is always present in ip header
:-

>
> Router drops a packet with a TTL value of 0. So when the control plane
> packet comes. it should be of TTL of 1.
> TTL will be only decremented on the outgoing interface and not the incoming
> interface. THe genreal logic says that the TTL of all control plane packets
> of all IGPS will be 1 and so when a router receives this control plane
> packet , it is destined to itself , it will update the OSPF or EIGRP RIB
> and
> in turn do the local computation for the best path .
>
> My question is whether the where does the TTL decrement happen ? My answer
> is outbound and for any other control plane packet it will be destined to
> itslef , so there will be no decrement in the TTL
>
> --
> With Warmest Regards,
>
> CCIE KID
> CCIE#29992 (Security)
>
>
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Received on Fri Oct 21 2011 - 14:50:40 ART