From: paul cosgrove (paul.cosgrove@gmail.com)
Date: Mon Dec 01 2008 - 07:38:22 ARST
Sorry, that link is dead. Not sure where eigrp tools can be found now.
Paul.
On Mon, Dec 1, 2008 at 9:32 AM, paul cosgrove <paul.cosgrove@gmail.com>wrote:
> Hi Scott,
>
> I was thinking of generating a packet as if it had passed over that number
> of hops, rather than using an actual network.
> You can get tools to do that kind of thing for most protocols and there is
> indeed one for eigrp:-
>
> http://www.hackingciscoexposed.com/tools/eigrp-tools.tar.gz
>
> Paul.
>
>
> On Mon, Dec 1, 2008 at 12:12 AM, Scott M Vermillion <
> scott_ccie_list@it-ag.com> wrote:
>
>> Hi again Paul!
>>
>> Hop count is actually carried in the EIGRP "IP Internal Routes TLV" and
>> the
>> "IP External Routes TLV" (Doyle Vol I is a great reference for this and
>> similar such topics). A router advertises a directly connected network
>> with
>> a hop count of zero and it's incremented from there by subsequent routers
>> learning of that network. When a router receiving an update increments
>> hop
>> count and the resulting value exceeds the locally configured max-hop
>> value,
>> it will be marked unreachable with a delay of 0xFFFFFF. I don't believe
>> that any update is sent on regarding that route with a delay of 0xFFFFFF -
>> I
>> believe this to be a completely local affair on a router-by-router basis.
>> But I could be wrong on that last count. Semantics at that point anyway.
>>
>> So I'd think that you'd either need a really big EIGRP network to test
>> what
>> the truly maximum implemented value might be or you'd need a means to
>> manipulate the "Hop Count" field in the TLV. I'm not aware that this can
>> be
>> manipulated in a route-map or any such thing...
>>
>> Cheers,
>>
>> Scott
>>
>>
>> -----Original Message-----
>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>> paul
>> cosgrove
>> Sent: Sunday, November 30, 2008 2:29 PM
>> To: Timothy Chin
>> Cc: Oleg Konovalov; Cisco certification
>> Subject: Re: EIGRP Maximum-hop
>>
>> p.s. I should have said we need to set maximum hops to 255 and generate a
>> packet as if it has passed over >224 hops. IPv6 hop limit, like TTL,
>> count
>> down not up.
>>
>>
>> On Sun, Nov 30, 2008 at 9:15 PM, paul cosgrove
>> <paul.cosgrove@gmail.com>wrote:
>>
>> > Hi Timothy,
>> >
>> > Thanks for the link. The paragraph which explains the 224 limit is
>> > incorrect in that the Transport Control Field does not exist in IP or
>> IPv6
>> > headers. The IPX TC header field functions like a hop count, and IPX
>> > packets with a TC of 16 are dropped, hence the need for a workaround if
>> > packets need to be sent further. The TTL in IP, or hop limit in IPv6
>> both
>> > allow 255 hops so there is no need to do that.
>> > The text looks to have been incorrectly copied from the old
>> documentation.
>> > The IPX workaround is explained in the old EIGRP paper at
>> >
>> http://ccrg.soe.ucsc.edu/<
>> http://ccrg.soe.ucsc.edu/publications/interop94.pd
>> f <http://ccrg.soe.ucsc.edu/publications/interop94.pdf>>
>> >
>> publications/interop94.pdf<
>> http://ccrg.soe.ucsc.edu/publications/interop94.p
>> df>
>> > and all the references I've seen to 224 appear to have been
>> derived/copied
>> > from that text. I've left a comment on the web page that it needs
>> updating.
>> >
>> > Since the documentation about the max hop limit is conflicting, some of
>> it
>> > must be incorrect. My guess is that the limit is indeed 255, but the
>> only
>> > way we will know for sure is to generate an eigrp packet with the hop
>> limit
>> > set above 224 and see if other routers consider the advertisement as
>> valid.
>> >
>> > Paul.
>> >
>> >
>> > On Sun, Nov 30, 2008 at 7:05 PM, Timothy Chin <Tim@1c-solutions.com
>> >wrote:
>> >
>> >> Hi,
>> >>
>> >>
>> >>
>> >> I know there has been conflicting information on this for awhile. I
>> don't
>> >> know why but the 12.4 command reference for IPv4 doesn't provide this
>> >> information but the IPv6 reference does specify the maximum network
>> width:
>> >>
>> >>
>> >>
>> >>
>> >>
>>
>> http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-eigrp_ps644
>> 1_TSD_Products_Configuration_Guide_Chapter.html<http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-eigrp_ps6441_TSD_Products_Configuration_Guide_Chapter.html>
>> >>
>> >>
>> >>
>> >> I don't see an update on the 12.4 IPv4 documentation regarding this but
>> >> going by previous releases I figure it would still be the same. From
>> what
>> I
>> >> know a maximum hop count of 255 can be configured but traffic would
>> only
>> >> traverse 224.
>> >>
>> >>
>> >> ------------------------------
>> >>
>> >> *From:* paul cosgrove [mailto:paul.cosgrove@gmail.com]
>> >> *Sent:* Sunday, November 30, 2008 12:56 PM
>> >> *To:* Timothy Chin
>> >> *Cc:* Oleg Konovalov; Cisco certification
>> >> *Subject:* Re: EIGRP Maximum-hop
>> >>
>> >>
>> >>
>> >> Hi Timothy,
>> >>
>> >> Just wondering if you have verified that?
>> >>
>> >> I know there is conflicting information about this point but the 12.4
>> >> command reference says the limit is 255.
>> >>
>> >>
>>
>> http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_eig2.html#
>> wp1011619<http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_eig2.html#wp1011619>
>> >>
>> >> Also the field is indeed 8 bits long in the packets (see figure 4-7).
>> >> http://oreilly.com/catalog/iprouting/chapter/ch04.html
>> >>
>> >> The following paper mentions the limit of 224, but only as a workaround
>> >> used on IPX networks to overcome limitations of IPX.
>> >> http://ccrg.soe.ucsc.edu/publications/interop94.pdf
>> >>
>> >> Paul.
>> >>
>> >> On Sun, Nov 30, 2008 at 12:49 PM, Timothy Chin <Tim@1c-solutions.com>
>> >> wrote:
>> >>
>> >> The maximum definable hop count is 255 but 224 hops is the true limit.
>> >>
>> >>
>> >>
>> >> -----Original Message-----
>> >> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
>> Of
>> >> Oleg Konovalov
>> >> Sent: Sunday, November 30, 2008 5:05 AM
>> >> To: Cisco certification
>> >> Subject: EIGRP Maximum-hop
>> >>
>> >> Hi all, I have question about EIGRP maximum hops, based on
>> >>
>> http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080
>> >>
>> 094cb<
>> http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a00
>> 80094cb>
>> >> 7.shtml we can set up maximum 220 hops, based on some CCNP materials it
>> >> is
>> >> 224. I test it on my router and 255 hops was OK.
>> >>
>> >> Routing Protocol is "eigrp 100"
>> >> Outgoing update filter list for all interfaces is not set
>> >> Incoming update filter list for all interfaces is not set
>> >> Default networks flagged in outgoing updates
>> >> Default networks accepted from incoming updates
>> >> EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
>> >> EIGRP maximum hopcount 100
>> >> EIGRP maximum metric variance 1
>> >> Redistributing: eigrp 100
>> >> EIGRP NSF-aware route hold timer is 240s
>> >> Automatic network summarization is in effect
>> >> Maximum path: 4
>> >> Routing for Networks:
>> >> Routing Information Sources:
>> >> Gateway Distance Last Update
>> >> Distance: internal 90 external 170
>> >>
>> >>
>> >> Then I have changed metric maximum-hops
>> >>
>> >> Router(config)#router eigrp 100
>> >> Router(config-router)#metric maximum-hops 255
>> >> Router(config-router)#end
>> >> Router#sh ip protocols
>> >> Routing Protocol is "eigrp 100"
>> >> Outgoing update filter list for all interfaces is not set
>> >> Incoming update filter list for all interfaces is not set
>> >> Default networks flagged in outgoing updates
>> >> Default networks accepted from incoming updates
>> >> EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
>> >> EIGRP maximum hopcount 255
>> >> EIGRP maximum metric variance 1
>> >> Redistributing: eigrp 100
>> >> EIGRP NSF-aware route hold timer is 240s
>> >> Automatic network summarization is in effect
>> >> Maximum path: 4
>> >> Routing for Networks:
>> >> Routing Information Sources:
>> >> Gateway Distance Last Update
>> >> Distance: internal 90 external 170
>> >>
>> >>
>> >> Blogs and organic groups at http://www.ccie.net
>> >>
>> >> _______________________________________________________________________
>> >> Subscription information may be found at:
>> >> http://www.groupstudy.com/list/CCIELab.html
>> >>
>> >>
>> >> Blogs and organic groups at http://www.ccie.net
>> >>
>> >> _______________________________________________________________________
>> >> Subscription information may be found at:
>> >> http://www.groupstudy.com/list/CCIELab.html
>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
>> _______________________________________________________________________
>> Subscription information may be found at:
>> http://www.groupstudy.com/list/CCIELab.html
Blogs and organic groups at http://www.ccie.net
This archive was generated by hypermail 2.1.4 : Thu Jan 01 2009 - 12:53:07 ARST