At 03:24 PM 4/25/01, Chuck Larrieu wrote:
>In answer to the question, yes the command is available under the eigrp
>process. Or at least it was when we were discussing this issue somewhere
>around a year ago. ;->
Can't see why!?
>Hey, PO, the only way that the hop count makes any sense is in terms of
>relating to the TTL You probably don't recall the thread, but I had found a
>document on EIGRP on CCO that made some bizarre claim about the EIGRP max
>diameter being 225 because of TCP limitations.
You can't believe everything you read.
TTL is a field in an IP header, not in a routing protocol packet.
Hop count is in IGRP packets (even though the metric is not based on it.)
Hop count is not in EIGRP packets.
I'm in a rush, but that's all I have to say for now! ;-)
Priscilla
>In any case, rightly or wrongly I have linked the max (E)IGRP diameter as
>255 because of the TTL. This may or may be a good reason for linking them.
>On the other hand, according to RFC 1812 ( unless I am mis-remembering my
>reading ) is that required router behaviour is to take any incoming packet,
>decrement the TTL by 1, and if the TTL value is still greater than zero,
>forward that packet. Otherwise, drop it. In the end, routing protocol
>packets are still IP packets, aren't they? Damn, now I have to break out my
>RFC's and go through this again!
>
>There is nothing in the (E)IGRP algorithms that calculate hop count, is
>there? Bandwidth, delay, reliability, load, MTU. I suppose that somewhere in
>the process the number of links crossed as well as the bandwidth of each of
>those links figures into the calculations.
>
>Let me ask the question with regards to another routing protocol - does OSPF
>have a hop count limit? If so, why? If not, why not?
>
>Come to think of it, most of the routing protocols have a TTL of 1 in the
>routing packet. With BGP one can manipulate this using the ebgp-multihop
>command. I can think of only one place to do TTL, and that's in the ip
>header. Debug ip packet seems to yield information about routing events as
>well as data events, does it not?
>
>Where's that bad boy Bob Vance when we need him? This discussion is right up
>his alley! ;->
>
>Chuck
>
>
>-----Original Message-----
>From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
>Priscilla Oppenheimer
>Sent: Wednesday, April 25, 2001 2:25 PM
>To: [EMAIL PROTECTED]
>Subject: RE: TTL [7:1700]
>
>At 08:22 PM 4/24/01, Chuck Larrieu wrote:
> >I'm not sure I understand the question, or the need.
> >
> >The TTL field is 8 bits, which gives a max value of 255.
> >
> >At this point, I believe that one's only options for manipulating TTL
would
> >be in terms of changing default hop count maximum for IGRP and EIGRP
>routing
> >protocols. I.e. the default distance for an (E)IGRP network is 100 ( 100
> >hops ) and this can be changed to a max of 255
>
>I would add that changing the hop count wouldn't actually manipulate the
>TTL at all. The hop count value affects the routing process and helps a
>router decide whether it should advertise a route. The TTL affects the
>forwarding process and helps a router decide whether it should forward a
>packet.
>
>With IGRP, the Cisco IOS software enforces a maximum diameter to the IGRP
>network. Routes whose hop counts exceed this diameter are not advertised.
>The default maximum diameter is 100 hops. The maximum diameter is 255 hops.
>
>To configure the maximum diameter, use the following command in router
>configuration mode:
>
>Router(config-router)#metric maximum-hops hops
>
>Interestingly enough, this command is not mentioned in the EIGRP
>documentation. It may not be supported or necessary in EIGRP. Anyone know?
>
>Priscilla
>
>
> >RFC 1812 specifies that all packets be dropped after the TTL is expired.
> >This is to keep packets from floating around forever. The process is
> >specifically described in terms of router behaviour.
> >
> >I suppose that various applications may manipulate the TTL value in
various
> >ways, but the fact is that the max value is still 255, and router stacks
>are
> >generally not configurable in the way you suggest.
> >
> >Am I understanding your question correctly?
> >
> >Chuck
> >
> >-----Original Message-----
> >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
>SH
> >Wesson
> >Sent: Tuesday, April 24, 2001 6:29 AM
> >To: [EMAIL PROTECTED]
> >Subject: TTL [7:1700]
> >
> >If I wanted to increase the TTL on a Cisco router, how can I do that?
> >
> >Thanks.
> >_________________________________________________________________
> >Get your FREE download of MSN Explorer at http://explorer.msn.com
> >FAQ, list archives, and subscription info:
> >http://www.groupstudy.com/list/cisco.html
> >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
> >FAQ, list archives, and subscription info:
> >http://www.groupstudy.com/list/cisco.html
> >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
>
>
>________________________
>
>Priscilla Oppenheimer
>http://www.priscilla.com
>FAQ, list archives, and subscription info:
>http://www.groupstudy.com/list/cisco.html
>Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
________________________
Priscilla Oppenheimer
http://www.priscilla.com
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=2004&t=1700
--------------------------------------------------
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
