From: Paul Cosgrove (paul.cosgrove@heanet.ie)
Date: Mon Sep 22 2008 - 13:45:56 ART
Hi Huan,
I found the following link which (briefly) describes how EIGRP handles
static routes pointed to connected interfaces:-
http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094cb7.shtml
Paul.
CCIE unnumbered wrote:
> Thank you for all the responses!
>
>
>
>
>
> Huan Pham wrote:
>
>> Hi Paul,
>>
>> You're correct about the behaviour of static route and network statement
>> in EIGRP! I did not know that EIGRP (and RIP as you said) treated Static
>> Routes that point to a connected interface similar as as Connected
>> Interfaces! Very interesting behaviour! I labbed up a simple scenario
>> and the behaviour is exactly as you said (although it is irrelevant to
>> the example in Doc CD, as the static routes in the Doc CD use next hop
>> IP address, instead of outgoing interfaces). However, I could not find
>> this behaviour documented anywhere yet. Could you pls give me any
>> pointer. Thanks.
>>
>> Thanks again for bringing this behaviour into my attention. This is what
>> we benifit from taking part in discussion of the high quality mailing
>> list such as GroupStudy.
>>
>>
>> R2#sh ip int brief | ex unass
>> Interface IP-Address OK? Method Status
>> Protocol
>> Serial1/1 23.0.0.2 YES manual up
>> up
>> R2#sh run
>> router eigrp 100
>> network 10.10.10.0 0.0.0.255
>> network 23.0.0.2 0.0.0.0
>> no auto-summary
>>
>> ip route 10.10.10.0 255.255.255.0 Null0
>>
>> R3#sh ip route eigrp
>> 10.0.0.0/24 is subnetted, 1 subnets
>> D 10.10.10.0 [90/2169856] via 23.0.0.2, 00:06:38, Serial1/3
>>
>>
>>
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>> paul cosgrove
>> Sent: Sunday, 21 September 2008 10:20 PM
>> To: Huan Pham
>> Cc: Gary Duncanson; Cisco certification; ccie.unnumbered@gmail.com
>> Subject: Re: Cisco DOCS confusion
>>
>> Hi Huan,
>>
>> You mentioned that 'network 0.0.0.0' with a static default route is a
>> special case, but actually the same behaviour is seen for any static
>> route pointing to a connected interface. Static routes pointing to
>> connected interfaces are treated like connected interfaces themselves by
>> EIGRP and RIP. If there is a matching network statement they will be
>> advertised. The default route is not treated any differently.
>>
>> The example config from the cisco site is poorly explained, and has a
>> few errors. Difficult to know if it was intended to show filtering, or
>> an auto summarisation problem as Gary suggested. The text suggests to
>> me that the number of lines in the acl, as well as the wildcard masks on
>> the acl and network statement are all errors.
>>
>> The example shows a config for a router which has two interfaces in
>> different major networks, 192.168.7.0 and 10.10.20.0. If auto
>> summarisation is enabled on the router being configured (though off by
>> default these days, it is not specifically disabled), then the
>> 10.10.10.0 route will not be advertised to the 192.168.7.x neighbor,
>> instead (without the distribute-list) it will receive 10.0.0.0/8.
>>
>> The distribute-list would stop this, so that only the two 192.168.x.x
>> redistributed routes are advertised. If you wanted all three advertised
>> you would have to disable auto summarisation.
>>
>> Paul.
>>
>> Huan Pham wrote:
>>
>>
>>> HI Gary,
>>>
>>> I do not have that book in front of me. The no auto-summary command is
>>>
>>>
>> to disable automatic summmarization of routes advertized to neighbors
>> at classfull boundary. This is not relevant to the wildcard mask
>> specified after the network statement.
>>
>>
>>> The IOS behaviour I see is that, if you do not specify the wildcard,
>>>
>>>
>> the router will convert it to the whole classfull network, and enables
>> EIGRP on all interfaces that belong to that classfull network.
>>
>>
>>> R1(config)#router ei 100
>>> R1(config-router)#no auto-summary
>>> R1(config-router)#net 150.1.1.0
>>> R1(config-router)#
>>>
>>> R1#sh run | s router
>>> router eigrp 100
>>> network 150.1.0.0
>>> no auto-summary
>>>
>>>
>>>
>>>
>>> --- On Sun, 9/21/08, Gary Duncanson <garyduncanson@btinternet.com>
>>>
>>>
>> wrote:
>>
>>
>>>
>>>
>>>
>>>> From: Gary Duncanson <garyduncanson@btinternet.com>
>>>> Subject: Re: Cisco DOCS confusion
>>>> To: "Huan Pham" <pnhuan@yahoo.com>
>>>> Cc: "Cisco certification" <ccielab@groupstudy.com>,
>>>> ccie.unnumbered@gmail.com
>>>> Date: Sunday, September 21, 2008, 4:53 AM You can also disable
>>>> automatic summarization in eigrp and get over the network wildcard
>>>> mask hassles to some extent.
>>>>
>>>> no auto-summary
>>>>
>>>> Doyle Vol I pp315-316
>>>>
>>>> I have seen a number of variants in practice lab examples.
>>>>
>>>>
>>>>
>>>> ----- Original Message -----
>>>> From: "Huan Pham" <pnhuan@yahoo.com>
>>>> To: <ccielab@groupstudy.com>; "CCIE
>>>> unnumbered" <ccie.unnumbered@gmail.com>
>>>> Sent: Saturday, September 20, 2008 11:12 AM
>>>> Subject: Re: Cisco DOCS confusion
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>> This is a terrible example in the DOC CD. I cannot
>>>>>
>>>>>
>>>>>
>>>> understand why it
>>>>
>>>>
>>>>
>>>>> exists in the DOC CD!!! It is just a terriblly wrong
>>>>>
>>>>>
>>>>>
>>>> example, in my
>>>>
>>>>
>>>>
>>>>> opinion.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>> (1) I thought all three routes were advertised by "network" command
>>>>>>
>>>>>>
>>
>>
>>>>>> under router eigrp 1
>>>>>>
>>>>>>
>>>>>>
>>>>> No, you are not correct. All three routes are
>>>>>
>>>>>
>>>>>
>>>> advertized by the
>>>>
>>>>
>>>>
>>>>> redistribute static command.
>>>>>
>>>>> In the EIGRP, similar to all IGP, the network command
>>>>>
>>>>>
>>>>>
>>>> is to specify what
>>>>
>>>>
>>>>
>>>>> interface(s) take part in the routing protocol. It is
>>>>>
>>>>>
>>>>>
>>>> not to advertize the
>>>>
>>>>
>>>>
>>>>> subnets specify by that statement.
>>>>>
>>>>> EIGRP also requires you to put the wildcard mask. If
>>>>>
>>>>>
>>>>>
>>>> you do not, then
>>>>
>>>>
>>>>
>>>>> EIGRP a classfull network is specified.
>>>>>
>>>>> In the example
>>>>>
>>>>> router eigrp 1
>>>>> network 10.10.10.0
>>>>>
>>>>> is the same as
>>>>>
>>>>> router eigrp 1
>>>>> network 10.0.0.0
>>>>>
>>>>> or
>>>>>
>>>>> router eigrp 1
>>>>> network 10.0.0.0 0.255.255.255
>>>>>
>>>>> In EIGRP there's one special case where the
>>>>>
>>>>>
>>>>>
>>>> network statement also
>>>>
>>>>
>>>>
>>>>> advertizes the route, is when you do network 0.0.0.0
>>>>>
>>>>>
>>>>>
>>>> and you have a static
>>>>
>>>>
>>>>
>>>>> default route. In this case, the network 0.0.0.0
>>>>>
>>>>>
>>>>>
>>>> statement also enables
>>>>
>>>>
>>>>
>>>>> EIGRP on all interfaces as well.
>>>>>
>>>>> router eigrp 1
>>>>> network 0.0.0.0
>>>>> ip route 0.0.0.0 0.0.0.0 null0
>>>>>
>>>>> In the DOC CD examle, these network statments for
>>>>>
>>>>>
>>>>>
>>>> 192.168.0.0 and
>>>>
>>>>
>>>>
>>>>> 10.10.10.0 have nothing to do with the usage of
>>>>>
>>>>>
>>>>>
>>>> distribute-list to control
>>>>
>>>>
>>>>
>>>>> redistribution from Static to EIGRP!
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>> (2) the access-list 3 permit 192.168.x.0 should
>>>>>>
>>>>>>
>>>>>>
>>>> have
>>>>
>>>>
>>>>
>>>>>> wildcard mask 0.0.0.255?
>>>>>>
>>>>>>
>>>>>>
>>>>> You are right. Doc CD is wrong.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>> (3) I thought all three routes were redistributed
>>>>>>
>>>>>>
>>>>>>
>>>> by the
>>>>
>>>>
>>>>
>>>>>> *redistribute
>>>>>> static* router configuration?
>>>>>>
>>>>>>
>>>>>>
>>>>> You are right. I do not know what they meant to
>>>>>
>>>>>
>>>>>
>>>> blocked here ;) Maybe they
>>>>
>>>>
>>>>
>>>>> mean "deny 10.10.10.0 0.0.0.255" to block
>>>>>
>>>>>
>>>>>
>>>> the last one (???!!!)
>>>>
>>>>
>>>>
>>>>>> (4) what does the *distribute-list 3 out static*
>>>>>>
>>>>>>
>>>>>>
>>>> command do
>>>>
>>>>
>>>>
>>>>>> in this case?
>>>>>>
>>>>>>
>>>>>>
>>>>> Nothing, unless they change the ACL 3 to block one of
>>>>>
>>>>>
>>>>>
>>>> the three subnets.
>>>>
>>>>
>>>>
>>>>> In that case, the one blocked by the ACL will not be
>>>>>
>>>>>
>>>>>
>>>> advertized into
>>>>
>>>>
>>>>
>>>>> EIGRP.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --- On Sat, 9/20/08, CCIE unnumbered
>>>>>
>>>>>
>>>>>
>>>> <ccie.unnumbered@gmail.com> wrote:
>>>>
>>>>
>>>>
>>>>>> From: CCIE unnumbered
>>>>>>
>>>>>>
>>>>>>
>>>> <ccie.unnumbered@gmail.com>
>>>>
>>>>
>>>>
>>>>>> Subject: Cisco DOCS confusion
>>>>>> To: ccielab@groupstudy.com
>>>>>> Date: Saturday, September 20, 2008, 3:20 PM Dear Groupstudy
>>>>>> Experts:
>>>>>>
>>>>>> Please find a digest from
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>> http://www.cisco.com/en/US/docs/ios/iproute/configuration/guide/irp_i
>>>> p_prot_indep_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1
>>>> 057083
>>>>
>>>>
>>>>
>>>>>> in the end of this message, and help me explain
>>>>>>
>>>>>>
>>>>>>
>>>> the
>>>>
>>>>
>>>>
>>>>>> description of the
>>>>>> section. (1) I thought all three routes were
>>>>>>
>>>>>>
>>>>>>
>>>> advertised by
>>>>
>>>>
>>>>
>>>>>> "network"
>>>>>> command under router eigrp 1
>>>>>> (2) the access-list 3 permit 192.168.x.0 should
>>>>>>
>>>>>>
>>>>>>
>>>> have
>>>>
>>>>
>>>>
>>>>>> wildcard mask 0.0.0.255?
>>>>>> (3) I thought all three routes were redistributed
>>>>>>
>>>>>>
>>>>>>
>>>> by the
>>>>
>>>>
>>>>
>>>>>> *redistribute
>>>>>> static* router configuration?
>>>>>> (4) what does the *distribute-list 3 out static*
>>>>>>
>>>>>>
>>>>>>
>>>> command do
>>>>
>>>>
>>>>
>>>>>> in this case?
>>>>>>
>>>>>> Static Routing Redistribution Example
>>>>>>
>>>>>> In the example that follows, three static routes
>>>>>>
>>>>>>
>>>>>>
>>>> are
>>>>
>>>>
>>>>
>>>>>> specified, two of which
>>>>>> are to be advertised. The static routes are
>>>>>>
>>>>>>
>>>>>>
>>>> created by
>>>>
>>>>
>>>>
>>>>>> specifying the
>>>>>> *redistribute
>>>>>> static* router configuration command and then
>>>>>>
>>>>>>
>>>>>>
>>>> specifying an
>>>>
>>>>
>>>>
>>>>>> access list that
>>>>>> allows only those two networks to be passed to the
>>>>>>
>>>>>>
>>>>>>
>>>> EIGRP
>>>>
>>>>
>>>>
>>>>>> process. Any
>>>>>> redistributed static routes should be sourced by a
>>>>>>
>>>>>>
>>>>>>
>>>> single
>>>>
>>>>
>>>>
>>>>>> router to minimize
>>>>>> the likelihood of creating a routing loop.
>>>>>>
>>>>>> Router(config)# *ip route 192.168.2.0
>>>>>>
>>>>>>
>>>>>>
>>>> 255.255.255.0
>>>>
>>>>
>>>>
>>>>>> 192.168.7.65
>>>>>> *
>>>>>>
>>>>>> Router(config)# *ip route 192.168.5.0
>>>>>>
>>>>>>
>>>>>>
>>>> 255.255.255.0
>>>>
>>>>
>>>>
>>>>>> 192.168.7.65
>>>>>> *
>>>>>>
>>>>>> Router(config)# *ip route 10.10.10.0
>>>>>>
>>>>>>
>>>>>>
>>>> 255.255.255.0
>>>>
>>>>
>>>>
>>>>>> 10.20.1.2
>>>>>> *
>>>>>>
>>>>>> Router(config)# *!
>>>>>> *
>>>>>>
>>>>>> Router(config)# *access-list 3 permit 192.168.2.0
>>>>>> 0.0.255.255
>>>>>> *
>>>>>>
>>>>>> Router(config)# *access-list 3 permit 192.168.5.0
>>>>>> 0.0.255.255
>>>>>> *
>>>>>>
>>>>>> Router(config)# *access-list 3 permit 10.10.10.0
>>>>>>
>>>>>>
>>>>>>
>>>> 0.0.0.255
>>>>
>>>>
>>>>
>>>>>> *
>>>>>>
>>>>>> Router(config)# *!
>>>>>> *
>>>>>>
>>>>>> Router(config)# *router eigrp 1
>>>>>> *
>>>>>>
>>>>>> Router(config-router)# *network 192.168.0.0
>>>>>> *
>>>>>>
>>>>>> Router(config-router)# *network 10.10.10.0
>>>>>> *
>>>>>>
>>>>>> Router(config-router)# *redistribute static
>>>>>>
>>>>>>
>>>>>>
>>>> metric 10000
>>>>
>>>>
>>>>
>>>>>> 100 255 1 1500
>>>>>> *
>>>>>>
>>>>>> Router(config-router)# *distribute-list 3 out
>>>>>>
>>>>>>
>>>>>>
>>>> static
>>>>
>>>>
>>>>
>>>>>> *
>>>>>>
>>>>>>
>>>>>> Thanks,
>>>>>> --
>>>>>> CCIE unnumbered
>>>>>>
>>>>>>
>>>>>> Blogs and organic groups at http://www.ccie.net
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>> _____________________________________________________________________
>>>> __
>>>>
>>>>
>>>>
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>>>>>>
>>>>>>
>>>>>>
>>>>> Blogs and organic groups at http://www.ccie.net
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>> _____________________________________________________________________
>>>> __
>>>>
>>>>
>>>>
>>>>> Subscription information may be found at:
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>>>>>
>>>>>
>>>>>
>>> Blogs and organic groups at http://www.ccie.net
>>>
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