The rip's limitation is if a route is more than 15 hop
away, it is considered unreachable.
I do not think the TTL is a problem, just like when
ping a destination across the world, you do not worry
about the TTL of your packets, normally.
Kent
--- Lance Simon <[EMAIL PROTECTED]> wrote:
> So, are you suggesting that the RIP update be passed
> through 16 router hops? I am
> not the routing protocol expert of this group, but I
> know that you will only
> update your neighboring router routers.
> This may not be a big deal, since rip updates are
> sent via a broadcast (v1) or
> multicast address (v2). But, every vendor puts in a
> ttl of _. I just want to
> know how a ttl of 1 works, when most routers
> decrement before looking at the
> packet.
>
> Lance
>
> Nimesh Vakharia wrote:
>
> > If I remember this right, RIP scales upto 16
> hops... after that you can
> > ICMP host unreachables.. so max TTL would be 16..
> >
> > Nimesh.
> >
> > On Mon, 5 Jun 2000, Lance Simon wrote:
> >
> > > Yes, I was wrong about it not being in the IP
> header. The ttl is in the ip
> > > header. RIP updates are transported over UDP
> port 520. Now, what do you
> > > think the ttl for a RIP update should be,
> Nimesh? And why?
> > >
> > > Nimesh Vakharia wrote:
> > >
> > > > It would be very interesting to see these
> traces. The switch must be doing
> > > > something very wierd. A UDP header consists of
> Source Port, Dest Port,
> > > > Length and the checksum... TTL's are usually
> L3 and a max TTL 2 indicates
> > > > somethings really screwed up.
> > > >
> > > > Nimesh.
> > > >
> > > > On Sun, 4 Jun 2000, Lance Simon wrote:
> > > >
> > > > > Actually, if the switch is routing, it will
> decrement the hop or ttl
> > > > > value. And the ttl on a RIP update is in
> the UDP header. If you are
> > > > > not convinced I will send you the traces.
> And finally, as Travis
> > > > > stated, a RIP update should only have max
> ttl of 2.
> > > > > Lance
> > > > >
> > > > > Cormac Long wrote:
> > > > >
> > > > > > Not sure what the nature of the problem is
> here, but
> > > > > > here are a couple of points to note:
> > > > > >
> > > > > > 1. The TTL field is in the IP header and
> not the UDP
> > > > > > header.
> > > > > >
> > > > > > 2. The TTL is only decremented after the
> packet
> > > > > > crosses a router hop ( a switch hop does
> NOT count).
> > > > > >
> > > > > > 3. The inital TTL=15, and it gets
> decremented after
> > > > > > that as it crosses routers. This makes it
> surprising
> > > > > > that you're seeing TTL=1 or 2. It implies
> alot of
> > > > > > router hops.
> > > > > >
> > > > > > Cormac
> > > > > >
> > > > > > Cormac Long, CCSI#21600
> > > > > > http://www.cormaclong.com
> > > > > >
> > > > > > --- Lance Simon <[EMAIL PROTECTED]>
> wrote:
> > > > > > > Hi group!
> > > > > > >
> > > > > > > I am a lurker at best here, but today I
> saw
> > > > > > > something that really
> > > > > > > puzzled me. While I was looking at a
> trace file I
> > > > > > > noticed something
> > > > > > > unusual about the ttl values for RIP
> updates on a
> > > > > > > PacketEngines switch.
> > > > > > > This switch is connected to a Cat5000
> and I had a
> > > > > > > sniffer in between the
> > > > > > >
> > > > > > > two.
> > > > > > > My understanding of RIP is that the ttl
> value = 2
> > > > > > > and that it is
> > > > > > > decremented as it enters a switch/router
> and then it
> > > > > > > is looked at.
> > > > > > > Therefore, a ttl=2 would become ttl=1
> before the
> > > > > > > packet is even looked
> > > > > > > at. If the ttl=1 it would become ttl=0
> and then,
> > > > > > > instead of being
> > > > > > > looked at, it would be discarded. Is
> this correct?
> > > > > > > First, let me say that the Packet
> Engines 2200
> > > > > > > switch is a very good box
> > > > > > >
> > > > > > > and it is communicating well with the
> Cat5k. The
> > > > > > > RIP updates are being
> > > > > > > handled well by both sides, but; when
> looking at
> > > > > > > the sniff, the ttl
> > > > > > > value from the packet Engines box is set
> to =1. How
> > > > > > > can this be?
> > > > > > > Do I totally misunderstand the UDP ttl
> value in
> > > > > > > relationship to RIP?
> > > > > > > Any insights would be helpful. BTW, I
> have got a
> > > > > > > call into a
> > > > > > > PacketEngines s/w engineer and am
> waiting for a
> > > > > > > response.
> > > > > > >
> > > > > > > Thanks,
> > > > > > >
> > > > > > > Lance
> > > > > > >
> > > > > > >
> > > > > > >
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> > > > > > =====
> > > > > > http://www.cormaclong.com
> > > > > >
> > > > > >
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