From: Howard Hooper (Howard.Hooper@dupre.co.uk)
Date: Mon Dec 01 2008 - 15:39:56 ARST
Hi All,
I've found another link for the EIGRP packet generator listed under
'EIGRP Tools' here
http://www.arhont.com/ViewPage7422.html?siteNodeId=3&languageId=1&conten
tId=-1
I carried out a few tests using dynamips on a linux machine connected to
an external router, as soon as the neighbor relationship is up between
them both I then used the packet generator to spoof update messages;
The following is an output from the packet generator config file, I
raised the 'Hop Count' to 224 as shown below, the output I received on
the router is below also.
!!!!!from config file!!!!!
#Metric
$k1="1";
$k2="0";
$k3="1";
$k4="0";
$k5="0";
$holdtime="15";
$mtu="1514";
$hopcount="224"
!
!
!!!!!!Output from router after receiving the Update message!!!!
!
15w1d: EIGRP: Received UPDATE on Vlan11 nbr 192.168.2.63
15w1d: AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ
un/rely 0/0
15w1d: IP-EIGRP(Default-IP-Routing-Table:1): Processing incoming UPDATE
packet
15w1d: IP-EIGRP(Default-IP-Routing-Table:1): Ext 192.168.67.201/32 M
4294967295
- 512 4294967295 SM 4294967295 - 512 100
!
!!!! nothing in the topology table !!!!!
IP-EIGRP Topology Table for AS(1)/ID(192.168.30.254)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 192.168.2.0/23, 1 successors, FD is 2816
via Connected, Vlan11
I then changed the hop count to a lower value and re-sent the update,
this time the router installed the route into it's routing table
15w1d: EIGRP: Received UPDATE on Vlan11 nbr 192.168.2.63
15w1d: AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ
un/rely 0/0
15w1d: IP-EIGRP(Default-IP-Routing-Table:1): Processing incoming UPDATE
packet
15w1d: IP-EIGRP(Default-IP-Routing-Table:1): Ext 192.168.67.201/32 M
2916 - 2560
356 SM 612 - 512 100
15w1d: DUAL: dest(192.168.67.201/32) not active
15w1d: DUAL: rcvupdate: 192.168.67.201/32 via 192.168.2.63 metric
2916/612
15w1d: DUAL: Find FS for dest 192.168.67.201/32. FD is 4294967295, RD is
4294967
295 found
15w1d: IP-EIGRP(Default-IP-Routing-Table:1): route installed for
192.168.67.201
()
15w1d: DUAL: RT installed 192.168.67.201/32 via 192.168.2.63
15w1d: DUAL: Send update about 192.168.67.201/32. Reason: metric chg
15w1d: DUAL: Send update about 192.168.67.201/32. Reason: new if
15w1d: EIGRP: Enqueueing UPDATE on Vlan11 iidbQ un/rely 0/1 serno 4-4
!
!!! Topology table !!!!
P 192.168.2.0/23, 1 successors, FD is 2816
via Connected, Vlan11
P 192.168.67.201/32, 1 successors, FD is 2916
via 192.168.2.63 (2916/612), Vlan11
I hope this helps.
Howard
---Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Gary Duncanson
Sent: 01 December 2008 11:11
To: paul cosgrove
Cc: Scott M Vermillion; tim@1c-solutions.com; Cisco certification
Subject: Re: EIGRP Maximum-hop
Paul,
All roads lead to dead link in Russia it seems apart from this link that
offers a download of a couple of tar files..
http://www.hacker-soft.net/Soft/Soft_2313.htm
For those on the list interested in TLV and don't have Doyle rhyshaden
has
some good schmatics of the headers..
http://www.rhyshaden.com/eigrp.htm
----- Original Message -----
From: "paul cosgrove" <paul.cosgrove@gmail.com>
To: "Scott M Vermillion" <scott_ccie_list@it-ag.com>
Cc: "Timothy Chin" <Tim@1c-solutions.com>; "Oleg Konovalov"
<OKonovalov@delta.ge>; "Cisco certification" <ccielab@groupstudy.com>
Sent: Monday, December 01, 2008 9:38 AM
Subject: Re: EIGRP Maximum-hop
> 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_p
s644
>>>
1_TSD_Products_Configuration_Guide_Chapter.html<http://www.cisco.com/en/
US/docs/ios/ipv6/configuration/guide/ip6-eigrp_ps6441_TSD_Products_Confi
guration_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.h
tml#
>>>
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
>>> >>
>>> >>
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