From: Gary Duncanson (gary.duncanson@googlemail.com)
Date: Thu Feb 28 2008 - 06:33:14 ARST
Check out Doyle Volume 1 p690 for good explanation and example of the RIP
0.0.0.0 behavior and advertising default network.
HTH
Gary
----- Original Message -----
From: "YourPal" <dearprudence28@gmail.com>
To: "Todd, Douglas M." <DTODD@partners.org>
Cc: <ccielab@groupstudy.com>
Sent: Wednesday, February 27, 2008 6:22 PM
Subject: Re: Issue advertising default route into RIP using "ip
default-network"
> Hi Douglas,
>
> Have a look at this link:
>
> http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094374.shtml#protocols
>
> It says:
> RIP advertises a route to 0.0.0.0 if a gateway of last resort is selected
> using the "ip default-network" command. This network specified in the "ip
> default-network" command need not be explicitly advertised under RIP.
>
>
> In my case, R3 has already flagged the static route 198.10.1.0/24 as
> candidate default route (as verified with "sh ip ro"). It has selected its
> gateway of last resort. So it should advertise a 0.0.0.0 into RIP domain
> (out interface s0/2) but it doesn't (as verified with "deb ip rip" on R3
> and
> "sh ip ro" on R1).
>
> I tried EIGRP. It seems to work. Please see the following configs and
> results.
>
> R1:
> !
> router eigrp 123
> network 131.108.99.1 0.0.0.0
> no auto-summary
> !
> ip classless
> !
>
> R3:
> !
> router eigrp 123
> redistribute static
> network 131.108.99.3 0.0.0.0
> no auto-summary
> !
> ip default-network 198.10.1.0
> ip route 198.10.1.0 255.255.255.0 161.44.192.2
> !
> ip classless
> !
>
> R3#sh ip ro
> Gateway of last resort is 161.44.192.2 to network 198.10.1.0
>
> 161.44.0.0/24 is subnetted, 1 subnets
> C 161.44.192.0 is directly connected, Serial0/3
> 131.108.0.0/24 is subnetted, 1 subnets
> C 131.108.99.0 is directly connected, Serial0/2
> S* 198.10.1.0/24 [1/0] via 161.44.192.2
>
> R1#sh ip ro
> Gateway of last resort is 131.108.99.3 to network 198.10.1.0
>
> 131.108.0.0/24 is subnetted, 1 subnets
> C 131.108.99.0 is directly connected, Serial0/0/1
> D*EX 198.10.1.0/24 [170/21024000] via 131.108.99.3, 03:29:07, Serial0/0/1
>
>
>
> Thank you.
>
> BR,
> Emil
>
>
> On 2/27/08, Todd, Douglas M. <DTODD@partners.org> wrote:
>>
>> Hi:
>> my 2c..
>>
>>
>> This is expected from what I believe. The use of the default-network
>> allows the
>> router to send all unknown destinations toward this network. This causes
>> a
>> recursive lookup on the router, this is the way it works. But the
>> default-network command works in conjuction with other routing
>> protocols -
>>
>>
>> CCO:
>> Cisco IOS software will source the default network with RIP if one of the
>> following conditions is met:
>> *The ip default-network command is configured.
>> *The default-information originate command is configured.
>> *The default route is learned via another routing protocol or static
>> route
>> and
>> then redistributed into RIP
>>
>>
>> This I see as the default network, not the default route..
>>
>>
>> For rip the default route needs to come from a nother protocol, other
>> wise
>> you
>> need to have a static route
>> ip route 0.0.0.0 0.0.0.0 1.1.1.1 and then redistribute that route w/in
>> rip.
>>
>> If you have eigrp/ospf/bgp sending a default route then you can
>> redistribute
>> that into rip (and use the default information originate command).
>>
>> Otherwise, you will just see the default network if the above conditions
>> exist.
>>
>> CCO:
>> If dynamic default information is not being passed to the software,
>> candidates
>> for the default route are specified with the ip default-network global
>> configuration command. In this usage, the ip default-network command
>> takes
>> an
>> unconnected network as an argument. If this network appears in the
>> routing
>> table
>> from any source (dynamic or static), it is flagged as a candidate default
>> route
>> and is a possible choice as the default route.
>> If the router has no interface on the default network, but does have a
>> route to
>> it, it considers this network as a candidate default path. The route
>> candidates
>> are examined and the best one is chosen, based on administrative distance
>> and
>> metric. The gateway to the best default path becomes the gateway of last
>> resort.
>>
>> So,
>>
>> Create an ospf domain and get a default route advertised into it, then
>> redistribute it into rip. You will then have a default route.
>>
>> DMT
>> ________________________________
>>
>> From: nobody@groupstudy.com on behalf of YourPal
>> Sent: Tue 2/26/2008 10:14 PM
>> To: ccielab@groupstudy.com
>> Subject: Issue advertising default route into RIP using "ip
>> default-network"
>>
>>
>>
>> Hi Group,
>>
>> I'm facing a problem advertising a default route into RIP using the "ip
>> default-network" command. My setup as follows:
>>
>> R1(s0/0/1)--------
>>
>> 131.108.99.0/24--------(s0/2)R3(s0/3)--------161.44.192.0/24--------(s0/0/1)R2
>>
>>
>> R1:
>> !
>> interface Serial0/0/1
>> ip address 131.108.99.1 255.255.255.0
>> clockrate 125000
>> !
>> router rip
>> version 2
>> network 131.108.0.0
>> no auto-summary
>> !
>> ip classless
>> !
>>
>> R2:
>> !
>> interface Loopback0
>> ip address 198.10.1.1 255.255.255.0
>> !
>> interface Serial0/0/1
>> ip address 161.44.192.2 255.255.255.0
>> clockrate 125000
>> !
>> ip classless
>> !
>> R3:
>> !
>> interface Serial0/2
>> ip address 131.108.99.3 255.255.255.0
>> !
>> interface Serial0/3
>> ip address 161.44.192.3 255.255.255.0
>> !
>> router rip
>> version 2
>> network 131.108.0.0
>> no auto-summary
>> !
>> ip default-network 198.10.1.0
>> ip route 198.10.1.0 255.255.255.0 161.44.192.2
>> !
>> ip classless
>> !
>>
>>
>> R3#sh ip ro
>> Gateway of last resort is 161.44.192.2 to network 198.10.1.0
>>
>> 161.44.0.0/24 is subnetted, 1 subnets
>> C 161.44.192.0 is directly connected, Serial0/3
>> 131.108.0.0/24 is subnetted, 1 subnets
>> C 131.108.99.0 is directly connected, Serial0/2
>> S* 198.10.1.0/24 [1/0] via 161.44.192.2
>>
>> R3#deb ip rip
>> RIP protocol debugging is on
>> *Mar 1 07:10:47.535: RIP: sending v2 update to 224.0.0.9 via Serial0/2 (
>> 131.108.99.3)
>> *Mar 1 07:10:47.535: RIP: build update entries - suppressing null update
>>
>> R1#sh ip ro
>> Gateway of last resort is not set
>>
>> 131.108.0.0/24 is subnetted, 1 subnets
>> C 131.108.99.0 is directly connected, Serial0/0/1
>>
>>
>>
>> I'm expecting R3 to advertise a default route into RIP as a result of the
>> "ip default-network" command. However it doesn't. Can anyone tell me what
>> am
>> I missing in my configuration?
>>
>>
>>
>> Thank you.
>>
>> BR,
>> Emil
>>
>> _______________________________________________________________________
>> Subscription information may be found at:
>> http://www.groupstudy.com/list/CCIELab.html
>>
>>
>>
>> The information transmitted in this electronic communication is intended
>> only
>> for the person or entity to whom it is addressed and may contain
>> confidential
>> and/or privileged material. Any review, retransmission, dissemination or
>> other
>> use of or taking of any action in reliance upon this information by
>> persons or
>> entities other than the intended recipient is prohibited. If you received
>> this
>> information in error, please contact the Compliance HelpLine at
>> 800-856-1983 and
>> properly dispose of this information.
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Sat Mar 01 2008 - 16:54:50 ARST