From: Howard Hooper (Howard.Hooper@dupre.co.uk)
Date: Tue Dec 02 2008 - 09:12:55 ARST
Hi,
I apologize for sending incorrect information, this is my fault for
rushing through this yesterday and not checking everything properly.
After changing the 'metric maximum-hops' value on the receiving router
to 255 a route sent with a hopcount of 254 is installed into the routing
table as shown below;
!
Routing Protocol is "eigrp 1"
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
!
!
15w2d: EIGRP: Received UPDATE on Vlan11 nbr 192.168.2.63
15w2d: AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ
un/rely 0/0
15w2d: IP-EIGRP(Default-IP-Routing-Table:1): Processing incoming UPDATE
packet
15w2d: IP-EIGRP(Default-IP-Routing-Table:1): Ext 192.168.67.201/32 M
2916 - 2560
356 SM 612 - 512 100
15w2d: DUAL: rcvupdate: 192.168.67.201/32 via 192.168.2.63 metric
2916/612
15w2d: DUAL: Find FS for dest 192.168.67.201/32. FD is 2916, RD is 2916
15w2d: DUAL: 192.168.2.63 metric 2916/612 found Dmin is 2916
15w2d: IP-EIGRP(Default-IP-Routing-Table:1): route installed for
192.168.67.201
()
15w2d: DUAL: RT installed 192.168.67.201/32 via 192.168.2.63
!
!
Router1#sh ip eigrp top 192.168.67.201 255.255.255.255
IP-EIGRP (AS 1): Topology entry for 192.168.67.201/32
State is Passive, Query origin flag is 1, 1 Successor(s), FD is 2916
Routing Descriptor Blocks:
192.168.2.63 (Vlan11), from 192.168.2.63, Send flag is 0x0
Composite metric is (2916/612), Route is External
Vector metric:
Minimum bandwidth is 1000000 Kbit
Total delay is 13 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 255
External data:
Originating router is 192.168.2.63
AS number of route is 1
External protocol is BGP, external metric is 0
Administrator tag is 0 (0x00000000)
A route with a received hopcount of 255 is not;
15w2d: EIGRP: Received UPDATE on Vlan11 nbr 192.168.2.63
15w2d: AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ
un/rely 0/0
15w2d: IP-EIGRP(Default-IP-Routing-Table:1): Processing incoming UPDATE
packet
15w2d: IP-EIGRP(Default-IP-Routing-Table:1): Int 192.168.69.201/32 M
4294967295
- 512 4294967295 SM 4294967295 - 512 100
As Paul mentioned below the default max hopcount is set to 100 so by
default a route received with a hop count of 99 is installed into the
routing table but anything > 100 is not;
!
Routing Protocol is "eigrp 1"
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
!
! Received route with hopcount of 99 !
!
15w2d: EIGRP: Received UPDATE on Vlan11 nbr 192.168.2.63
15w2d: AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ
un/rely 0/0
15w2d: IP-EIGRP(Default-IP-Routing-Table:1): Processing incoming UPDATE
packet
15w2d: IP-EIGRP(Default-IP-Routing-Table:1): Int 192.168.67.201/32 M
2916 - 2560
356 SM 612 - 512 100
15w2d: DUAL: dest(192.168.67.201/32) not active
15w2d: DUAL: rcvupdate: 192.168.67.201/32 via 192.168.2.63 metric
2916/612
15w2d: DUAL: Find FS for dest 192.168.67.201/32. FD is 4294967295, RD is
4294967
295 found
15w2d: IP-EIGRP(Default-IP-Routing-Table:1): route installed for
192.168.67.201
()
15w2d: DUAL: RT installed 192.168.67.201/32 via 192.168.2.63
15w2d: DUAL: Send update about 192.168.67.201/32. Reason: metric chg
15w2d: DUAL: Send update about 192.168.67.201/32. Reason: new if
15w2d: EIGRP: Enqueueing UPDATE on Vlan11 iidbQ un/rely 0/1 serno 3-3
!
!
Router#sh ip eigrp top 192.168.67.201 255.255.255.255
IP-EIGRP (AS 1): Topology entry for 192.168.67.201/32
State is Passive, Query origin flag is 1, 1 Successor(s), FD is 2916
Routing Descriptor Blocks:
192.168.2.63 (Vlan11), from 192.168.2.63, Send flag is 0x0
Composite metric is (2916/612), Route is Internal
Vector metric:
Minimum bandwidth is 1000000 Kbit
Total delay is 13 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 100
!
A route with a received hopcount of 100+ isn't installed;
!
15w2d: EIGRP: Received UPDATE on Vlan11 nbr 192.168.2.63
15w2d: AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ
un/rely 0/0
15w2d: IP-EIGRP(Default-IP-Routing-Table:1): Processing incoming UPDATE
packet
15w2d: IP-EIGRP(Default-IP-Routing-Table:1): Int 192.168.67.201/32 M
4294967295
- 512 4294967295 SM 4294967295 - 512 100
Sorry again, please let me know if you would like me to test anything
else for this
Howard
From: paul cosgrove [mailto:paul.cosgrove@gmail.com]
Sent: 02 December 2008 02:23
To: Howard Hooper
Cc: Gary Duncanson; ccielab@groupstudy.com
Subject: Re: EIGRP Maximum-hop
Hi Howard,
That helps a lot, many thanks for checking. I suppose to completely
close this off you could check that 223 is accepted (if you haven't
already). You might also confirm that you increased the eigrp metric
maximum-hops to 255. The default is 100 according to the command
reference.
Paul.
On Mon, Dec 1, 2008 at 5:39 PM, Howard Hooper
<Howard.Hooper@dupre.co.uk> wrote:
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
<http://www.arhont.com/ViewPage7422.html?siteNodeId=3&languageId=1&conte
ntId=-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
<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_Confi
guration_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.h
tml#
>>>
wp1011619<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
>>> >>
>>> >>
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