From: Pavel Bykov (slidersv@gmail.com)
Date: Tue Nov 18 2008 - 23:57:34 ARST
Scott, It is clear that things just got a bit confused.
There were more concepts at once, and I wanted just to clarify Cisco's
statement if anyone got wondering.
What I meant was that in the case of "Ra <-> Rb <-> Rc" setup and RIP
enabled on relevant interfaces that interconnect routers, if you would type
"ip default-network x.x.x.x" command on Ra, RIP would *automatically*
generate a *default route* and send it to Rb and Rc.
So yes, I do agree with your statement: "not anything to do with a **
default-network**, per se". I just wanted additionaly clarify Cisco's
statement about "automatization"
On Wed, Nov 19, 2008 at 2:46 AM, Scott M Vermillion <
scott_ccie_list@it-ag.com> wrote:
> Hey Pavel,
>
>
>
> I gotta run just now so I won't be around to carry the conversation on for
> at least several hours, if not until tomorrow, but I've read and re-read
> your final statement below:
>
>
>
> > This refers to RIP and EIGRP protocols which do redistribute default
> route automatically, if "ip default-network" command is present.
>
> Trying to figure out if I'm misreading you or if I disagree with what
> you've said. The whole **default-network** thing tends to get slightly
> convoluted if you're not somewhat careful about the use of the terms
> "redistribute," "propagate," "generate," "default-network," and "
> 0.0.0.0/0." The original question, as I understood it, had to do with **
> redistribution** of RIP into OSPF, and the subsequent **generation** and *
> *propagation** (or lack thereof) of **0.0.0.0/0** into OSPF not anything
> to do with a **default-network**, per se. Example lab I just threw up
> (and, in retrospect, I confess that a better lab would have had an
> additional router Rd out to the right of Rc for a couple of different
> reasons, but I'm in a bit of a rush this afternoon and this was something I
> had handy):
>
>
>
> Ra <-> 192.168.1.0 <->Rb<->192.168.2.0<->Rc
>
>
>
> I run RIP on 192.168.1.0/24 between Ra and Rb. I run OSPF on
> 192.168.2.0/24 between Rb and Rc. On Rc I issue the following under OSPF
> config:
>
>
>
> 'default-inf orig always'
>
>
>
> On Rb I see the following:
>
>
>
> Rb(config-router)#do sh ip route
>
> Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
>
> D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
>
> N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
>
> E1 - OSPF external type 1, E2 - OSPF external type 2
>
> i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS
> level-2
>
> ia - IS-IS inter area, * - candidate default, U - per-user static
> route
>
> o - ODR, P - periodic downloaded static route
>
>
>
> Gateway of last resort is 192.168.2.2 to network 0.0.0.0
>
>
>
> C 192.168.1.0 is directly connected, Serial0/0
>
> 192.168.2.0/30 is subnetted, 1 subnets
>
> C 192.168.2.0 is directly connected, Serial0/1
>
> O*E2 0.0.0.0/0 [110/1] via 192.168.2.2, 00:00:10, Serial0/1
>
>
>
>
>
> On Ra, thus far, I see:
>
>
>
> Ra#sh ip route
>
> Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
>
> D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
>
> N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
>
> E1 - OSPF external type 1, E2 - OSPF external type 2
>
> i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS
> level-2
>
> ia - IS-IS inter area, * - candidate default, U - per-user static
> route
>
> o - ODR, P - periodic downloaded static route
>
>
>
> Gateway of last resort is not set
>
>
>
> 192.168.1.0/30 is subnetted, 1 subnets
>
> C 192.168.1.0 is directly connected, Serial1/0
>
>
>
>
>
> Now on Rb I issue the following under RIP config:
>
>
>
> Rb(config-router)#redist ospf 100 met 8
>
>
>
> Now on Ra I see:
>
>
>
> Ra#sh ip route
>
> Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
>
> D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
>
> N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
>
> E1 - OSPF external type 1, E2 - OSPF external type 2
>
> i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS
> level-2
>
> ia - IS-IS inter area, * - candidate default, U - per-user static
> route
>
> o - ODR, P - periodic downloaded static route
>
>
>
> Gateway of last resort is 192.168.1.2 to network 0.0.0.0
>
>
>
> 192.168.1.0/30 is subnetted, 1 subnets
>
> C 192.168.1.0 is directly connected, Serial1/0
>
> R 192.168.2.0/24 [120/8] via 192.168.1.2, 00:00:01, Serial1/0
>
> R* 0.0.0.0/0 [120/8] via 192.168.1.2, 00:00:01, Serial1/0
>
>
>
>
>
> Note the following on Ra and Rb:
>
>
>
> Ra#sh run | inc default-network
>
>
>
> (no output)
>
>
>
> Rb#sh run | inc default-network
>
>
>
> (no output)
>
>
>
> Now, just to round things out (and wind up back where the OP was), if I
> flip the whole thing around, eliminate the 'default-inf orig always' on Rc,
> do an 'ip route 0.0.0.0 0.0.0.0 nul0' on Ra, redistribute static into RIP
> on Ra, then redistribute RIP into OSPF on Rb, I see no default route on Rc
> until I issue the 'default-inf orig' on Rb. Also note that my static **
> 0.0.0.0/0** route to nul0 **redistributed** at Ra is **propagated** via
> RIP to Rb, regardless of any **default-network** configuration.
>
>
>
> So **redistribution** and **propagation** of **0.0.0.0/0** routes into RIP
> (and, IIRC, EIGRP as well) is no problem and does not require any specific
> additional configuration (as does OSPF, hence the excerpt earlier posted).
> This is a reasonably good document that I refer back to whenever I forget
> the nuances of **default-networks** and use/applicability of the 'ip
> default-network' command in various contexts:
>
>
>
>
>
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094374.
shtml
>
>
>
> Regards,
>
>
> Scott
>
>
>
>
>
>
>
> *From:* Pavel Bykov [mailto:slidersv@gmail.com]
> *Sent:* Tuesday, November 18, 2008 4:07 PM
> *To:* Scott M Vermillion
> *Cc:* Sachin D; Cisco certification
> *Subject:* Re: Redistributing Default route
>
>
>
> Just FYI, in Scott's excerpt it is mentioned that "By default, in normal
> areas OSPF routers don't generate default routes into
> their routing domains, even if one exists."
>
> This refers to RIP and EIGRP protocols which do redistribute default route
> automatically, if "ip default-network" command is present.
>
> On Tue, Nov 18, 2008 at 11:06 PM, Scott M Vermillion <
> scott_ccie_list@it-ag.com> wrote:
>
> From:
>
>
>
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a74
>
.shtml<http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080
094a74.shtml>
>
> "Normal Areas
>
> By default, in normal areas OSPF routers don't generate default routes into
> their routing domains, even if one exists. To have an OSPF router generate
> a
> default route, use the default-information originate [always] [metric
> metric-value] [metric-type type-value] [route-map map-name] command in the
> OSPF router configuration mode. This generates an external Type-2 link with
> link-state ID 0.0.0.0 and network mask 0.0.0.0, which makes the router an
> ASBR."
>
> Cheers,
>
> Scott
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Sachin D
> Sent: Tuesday, November 18, 2008 9:35 AM
> To: Cisco certification
> Subject: Redistributing Default route
>
> Hi
>
> Need help on the below redistribution problem
>
>
>
> _ _ _ _ _ _ _ _ _ _ _ _ _
> | | |
> | RIP | OSPF |
> | | |
> R1<------------>R|2<----------->R3
> | | |
> | | |
> | _ _ _ _ _ _ _ | _ _ _ _ _ _ _ |
>
>
>
> In the above topology
> R2 is connected to R1 and R3.
> R1 and R2 are running RIP,
> R2 and R3 are running OSPF
>
> R1 is sending only default route to R2 via RIP
>
> Hence R2 has only 1 route for RIP subnets
> R* 0.0.0.0/0 [120/1] via x.x.x.x, 00:00:03,
>
> But when I am redistributing RIP into OSPF this default route is not
> getting
> redistributed into OSPF i.e R3 is not learning this default route.
>
> On the vice versa if default is generated in OSPF i.e by R3 and
> redistributed in RIP on R2 default route is passed to R1 i.e R1 learns the
> default route.
>
> Is there any concept I am missing here ?
>
> Why the default route is not getting redistributed into OSPF from RIP ?
>
>
> Regards
>
>
> Blogs and organic groups at http://www.ccie.net
>
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>
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>
> _______________________________________________________________________
> Subscription information may be found at:
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>
>
>
>
>
>
>
>
>
> --
> Pavel Bykov
> -------------------------------------------------
> Stop the braindumps!
> http://www.stopbraindumps.com/
>
-- Pavel Bykov ------------------------------------------------- Stop the braindumps! http://www.stopbraindumps.com/Blogs and organic groups at http://www.ccie.net
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