From: Ronnie Angello (ronnie.angello@gmail.com)
Date: Thu Dec 21 2006 - 15:18:57 ART
eBGP requires that neighbors are directly connected (addresses in neighbor
command are in same subnet). If you are configuring eBGP peering using
loopback addresses that are in different subnets, then you need to use the
neighbor ebgp-multihop command to change the TTL.
On 12/21/06, Iamgoingtobeaccie Iamgoingtobeaccie
<heyiamgoingtobeaccie@yahoo.co.in>
wrote:
>
> Hi,
> Thanks a lot.If the router decrements the TTL when it forwards,in
> the case of EBGP even the directly connected neighbor will not receive the
> packet as the TTL is 1.So EBGP's TTL is not 1???
>
> *Ronnie Angello <ronnie.angello@gmail.com >* wrote:
>
> RFC 1812, page 84:
>
> A router MUST generate a Time Exceeded message Code 0 (In Transit) when it
> discards a packet due to an expired TTL field. A router MAY have a
> per-interface option to disable origination of these messages on that
> interface, but that option MUST default to allowing the messages to be
> originated.
>
> RFC 1812, page 85:
>
> The Time-to-Live (TTL) field of the IP header is defined to be a timer
> limiting the lifetime of a datagram. When a router *forwards* a packet, it
> MUST reduce the TTL by at least one. If it holds a packet for more than one
> second, it MAY decrement the TTL by one for each second.
>
>
>
> On 12/20/06, Nawaz, Ajaz < Ajaz.Nawaz@bskyb.com > wrote:
> >
> > Tim
> >
> > So what occurs when it receives an update with TTL of two or three for
> > example?
> >
> > Are you suggesting it decrements that once for it's own use?
> >
> > What happens when it forwards this update to an onwards hop?
> >
> > Ajaz
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> > Tim
> > Sent: 20 December 2006 16:08
> > To: Nawaz, Ajaz; 'Iamgoingtobeaccie Iamgoingtobeaccie';
> > ccielab@groupstudy.com
> > Subject: RE: TTL
> >
> > Ajar,
> >
> > I'm pretty sure the TTL is decremented on Ingress. When a router
> > receives a
> > packet with a TTL of 1, the TTL is decremented making the TTL 0 and
> > causing
> > the router to send icmp time-exceeded message back.
> >
> > Please correct me if I'm mistaken.
> >
> > Thanks, Tim
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> > Nawaz, Ajaz
> > Sent: Wednesday, December 20, 2006 5:48 AM
> > To: Iamgoingtobeaccie Iamgoingtobeaccie; ccielab@groupstudy.com
> > Subject: RE: TTL
> >
> > Egress. You can prove it easily through testing.
> >
> > Hth
> > Ajaz Nawaz
> > CCIE#15721
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> > sabrina pittarel
> > Sent: 20 December 2006 06:52
> > To: Iamgoingtobeaccie Iamgoingtobeaccie; ccielab@groupstudy.com
> > Subject: Re: TTL
> >
> > Hi,
> > let's put it in this way...a router will never forward a packet that has
> >
> > been received with TTL equal to 0 or 1
> >
> > Sabrina
> >
> > ----- Original Message ----
> > From: Iamgoingtobeaccie Iamgoingtobeaccie <heyiamgoingtobeaccie@yahoo.co.in
> > >
> > To: ccielab@groupstudy.com
> > Sent: Tuesday, December 19, 2006 5:29:43 AM
> > Subject: TTL
> >
> > GS,
> > Can someone let me know where does the TTL get
> > decremented? Is it on the ingress of the receiving router or on the
> > egress
> > of
> > the sending router.
> >
> > When I configure EBGP between two routers with
> > their loopback IP addresses and enable 'debug ip packet',I am not seeing
> > any
> > packet coming in.So I assume that the TTL is decremented on the egress
> > interface of the sending router.Can someone confirm.
> >
> >
> >
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