Subject: RE: ttl = 255 and scope limited to lan ..why?

From: "A. K. Srikanth" <[email-masked]>
Date: Fri, 20 Jul 2001 14:02:24 -0400

Well the point is that if I sent a packet with TTL 3 from 2 hops away it
will be 1 by the time it reaches the router in  question..The bottomline
being it is not possible to tell how many hops (routers) a packet has been
through when it reaches you with a TTL of 1 whereas you can always tell that
it has not gone through a router if the packet has a TTL of 255 when it
reaches you.

Thanks,
Srikanth
> 
> 
> 
> > -----Original Message-----
> > From: Vikram [mailto:[email-masked]]
> > Sent: Friday, July 20, 2001 1:26 PM
> > To: Peter Hunt
> > Cc: [email-masked]
> > Subject: Re: ttl = 255 and scope limited to lan ..why? 
> > 
> > 
> > well if you send out pkts with ttl=1 in first place, it will 
> > not travel
> > more than one hop anyways. 
> > 
> > Also if you are a multicast router then you shhould never forward a
> > datagram with addresses of 244.0.0.x as 
> > destination,regardless of ttl. 
> > 
> > So the possibility of originating from more than one hop away doesnt
> > exist ie receving a misconfigured packet.
> > 
> > And besides,the vrrp pkt shld also clear numerous other checks to be
> > accepted as a valid vrrp pkt- ie Authenication issues.
> > 
> > Vikram
> > 
> > --- Peter Hunt <[email-masked]> wrote:
> > > > RFC says that ttl shld always be set to 255 in vrrp 
> pkt. and also
> > > that
> > > > the scope of each VR is restricted to a single lan. If 
> that is the
> > > case
> > > > wouldnt it better if the ttl was set to 1 instead?
> > > 
> > > It's possible that a packet with ttl of 1 originated from 
> > more than 1
> > > hop away. So it would be possible to inject protocol packets from
> > > another
> > > network.
> > > 
> > > By requiring a ttl of 255, you can ensure that protocol packets
> > > weren't
> > > forwarded from another network.
> > > 
> > > 	Peter.
> > > 
> > 
> > 
> > =====
> > ----
> > NO sense being pessimistic. It wouldnt work anyway
> > 
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>