02-25-2012 11:21 AM - edited 03-07-2019 05:11 AM
Hi,
I was reading this statement
EIGRP does not add static routes to the EIGRP topology table unless that routes are
redistributed.
Say Router A has direct connection to Router B.
And Router A fa int IP is 192.168.50.2
Router B has int IP 192.168.50.3
So this mean that if router A has default route like 0.0.0.0 0.0.0.0.0 192.168.50.3
and if i do the sh ip eigrp topology on the router A
it still shows route to
192.168.50.0 subnet?
Can someone please explain me why this happened?
thanks
mahesh
Solved! Go to Solution.
02-25-2012 12:31 PM
I may not be understanding fully either -- but you are asking if Router A will still show static default route in its routing table without the static redistribute command? The answer here would be Yes. Your routing table would show a static default route, any directly connected routes, and in addition any other routes learned from EIGRP.
With regard to why you are seeing the 192.168.50.2/31 route in Router A's EIGRP topology when you don't have the network statement in Router A's EIGRP configuration, is there a network statement that would match this network in the other directly-connected router (aka Router B)?
Matt
02-25-2012 03:04 PM
Hi Mahesh,
So as per above we can say that Router A shows the default route right???????????
Yes. Now the default route is being injected into EIGRP from another router and advertised to Router A.
IT is inaccessible because it has higher Admin dustance then connected router right?
Not entirely. It is inaccessible because it has a higher administrative distance than the static default route already present in your routing table in this case.
By both routes i mean 192.168.50.0.
The "192.168.50.0/31" is just a heading - a title - in the printout, not a real network. There is really only one 192.168.50.x network in your routing table - the 192.168.50.2/31. The title "192.168.50.0/31" means that all subnets of the once-classful network 192.168.50.0 are having the netmask of /31 and are listed below the title. Once again, the "192.168.50.0/31" in your routing table is not a network.
Best regards,
Peter
02-25-2012 11:27 AM
Hi Mahesh,
I am not sure if I understand what you find surprising in the EIGRP behavior. The 192.168.50.0 subnet should be present in your EIGRP topology because it is a directly connected network on router A that has been included into EIGRP using the network command. However, the static default route will not be in the EIGRP's topology table unless you use the redistribute static command.
Perhaps you could try to explain the issue in different words.
Best regards,
Peter
02-25-2012 12:24 PM
Hi Peter,
Thanks for reply.
192.168.50.x subnet has not been included in network eigrp command using Router A.
Here is config on A router
router eigrp 90
passive-interface default
no passive-interface Serial0/0
network 10.1.0.0 0.0.255.255
network 15.15.15.15 0.0.0.0
network 172.30.0.0
no auto-summary
ip route 0.0.0.0 0.0.0.0 192.168.50.3
sh ip eigrp topology shows
P 192.168.50.2/31, 0 successors, FD is Inaccessible**********************************
via 10.1.24.2 (26137600/25625600), Serial0/0 P 192.168.50.2/31, 0 successors, FD is Inaccessible
via 10.1.24.2 (26137600/25625600), Serial0/0
I have to static redistribute command on the Router A still it shows static default route on Router A?
is this normal behaviour?
thanks
mahesh
02-25-2012 12:31 PM
I may not be understanding fully either -- but you are asking if Router A will still show static default route in its routing table without the static redistribute command? The answer here would be Yes. Your routing table would show a static default route, any directly connected routes, and in addition any other routes learned from EIGRP.
With regard to why you are seeing the 192.168.50.2/31 route in Router A's EIGRP topology when you don't have the network statement in Router A's EIGRP configuration, is there a network statement that would match this network in the other directly-connected router (aka Router B)?
Matt
02-25-2012 12:32 PM
Hi Mahesh,
I have to static redistribute command on the Router A still it shows static default route on Router A?
is this normal behaviour?
Yes, that is normal. Even if routes are redistributed into a different routing protocol, their original protocol does not change in your routing table. It would not work otherwise - just imagine that your static default route would change to an EIGRP route after redistribution. That would mean that the redistribute static command no longer applies to it because it is not static anymore - and it would fall out from EIGRP, becoming static again, and the entire cycle repeating all over again.
This is a common misunderstanding with redistributed routes. Remember: on the router performing redistribution, the source protocol of redistributed routes does not change.
Regarding the network 192.168.50.2/31, if Router A does not include it into EIGRP using the network command then I assume that Router B does. Am I correct in this assumption?
Best regards,
Peter
02-25-2012 12:38 PM
Well said Peter - stated more clearly than mine I think!
02-25-2012 12:48 PM
Hello Matt,
Thank you very much! I am glad you joined the thread. And it is nice to see how similarly we both think
Best regards,
Peter
02-25-2012 12:49 PM
Hi Peter,
Thanks for reply.
I check the Router B it also has no network command 192.168.50.0 Router EIGRP config.
Correction below for last post--in bold - no----
I have no static redistribute command on the Router A still it shows static default route on Router As Eigrp topology
table.is this normal behaviour?
So my understanding is that for above statement to be true its ok to have
192.168.50.2 in EIGRP topology table without redistribute eigrp static command?
mahesh
02-25-2012 12:57 PM
Mahesh,
There are too many unclear things about how exactly are your routers interconnected and how they are configured. Please be so kind to post the full configuration of both routers and if possible, draw a quick sketch of your network - or at least include the show cdp neighbors output from both routers. Thank you!
Best regards,
Peter
02-25-2012 01:33 PM
Hi Peter,
Thanks for reply.
Seems i have found the issue
Router A connects to Router B
Also Router A has EIGRP connection to Router C.
Router A = BB
BB#sh cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater
Device ID Local Intrfce Holdtme Capability Platform Port ID
3550SMIA.manveer.com
Fas 0/0 150 R S I WS-C3550- Fas 0/13
2650XM Ser 0/0 142 R S I 2650XM Ser 0/1
Router B ===3550SMIA
3550SMIA#sh cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone
Device ID Local Intrfce Holdtme Capability Platform Port ID
BB Fas 0/13 144 R S I 2650 Fas 0/0
2650XM Fas 0/4 144 R S I 2650XM Fas 0/0
3550SMIB Gig 0/1 132 R S I WS-C3550- Gig 0/1
3550SMIB Gig 0/2 132 R S I WS-C3550- Gig 0/2
2691Router
Fas 0/11 135 R S I 2691 Fas 0/1
2650Router Fas 0/1 162 R S 2650 Fas 0/0
Router C =====2650XM
2650XM#sh cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater
Device ID Local Intrfce Holdtme Capability Platform Port ID
BB Ser 0/1 120 R S I 2650 Ser 0/0
3550SMIA.manveer.com
Fas 0/0 174 R S I WS-C3550- Fas 0/4
2620Router Fas 1/0 122 R 2620 Fas 1/0
2620Router Ser 0/0 148 R 2620 Ser 0/0
Router C is doing redistribution of EIGRP into OSPF and OSPF into EIGRP
Router C config
router eigrp 90
redistribute ospf 1 metric 100 100 100 100 100**********************************************
When i remove the above redistribute command from Router C then on Router A if i do
sh ip eigrp topology
sh ip eigrp topology
IP-EIGRP Topology Table for AS(90)/ID(172.30.8.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 15.0.0.0/8, 1 successors, FD is 281600
via Connected, Ethernet1/0
P 10.1.24.0/30, 1 successors, FD is 2178560
via Connected, Serial0/0
P 172.30.2.0/24, 1 successors, FD is 128256
via Connected, Loopback2
P 172.30.3.0/24, 1 successors, FD is 128256
via Connected, Loopback3
P 172.30.0.0/24, 1 successors, FD is 128256
via Connected, Loopback0
P 172.30.1.0/24, 1 successors, FD is 128256
via Connected, Loopback1
P 172.30.6.0/24, 1 successors, FD is 128256
via Connected, Loopback6
P 172.30.7.0/24, 1 successors, FD is 128256
via Connected, Loopback7
P 172.30.4.0/24, 1 successors, FD is 128256
via Connected, Loopback4
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 172.30.5.0/24, 1 successors, FD is 128256
via Connected, Loopback5
P 172.30.8.0/24, 1 successors, FD is 128256
via Connected, Loopback8
As above now it does not show static default route of 192.168.50.2.
When i put the redistribute osp 1 command back on router C
Router A shows
P 192.168.50.2/31, 0 successors, FD is Inaccessible
via 10.1.24.2 (26137600/25625600), Serial0/0 P 192.168.50.2/31, 0 successors, FD is Inaccessible
via 10.1.24.2 (26137600/25625600), Serial0/0
Does it make sense peter?
Also it shows that while redistributing into EIGRP even if we do not put command
redistribute eigrp static then also it shows static default route in eigrp topology table of router A correct?
thanks
mahesh
02-25-2012 01:58 PM
Hello Mahesh,
The information from you are still very partial and they do not give us a good overview of how your network looks like, where do the individual routing protocols run and how are individual routers configured. I am only doing my best guess here.
As above now it does not show static default route of 192.168.50.2.
But that is not a "static default route" at all, my friend. A static default route must be a network 0.0.0.0/0. No other network can be called a default route. The 192.168.50.2 may theoretically be a next hop towards the default route but never a default route itself.
Now, what you see here when activating and deactivating the redistribution from OSPF to EIGRP is relatively simple. OSPF somehow knows about the network 192.168.50.2/31. When you redistribute from OSPF to EIGRP, information about this network is injected into EIGRP and is propagated to router A. However, when router A's EIGRP tries to enter this network into the routing table, it find out that the network 192.168.50.2/31 is already present in the routing table as a directly connected route. Because the directly connected route 192.168.50.2/31 has the administrative distance of 0, it is considered more trustworthy than the EIGRP-learned external network with administrative distance of 170. That is the reason why the 192.168.50.2/31 is present in your topology table marked as Inaccessible.
Best regards,
Peter
02-25-2012 02:28 PM
Hi Peter,
thanks for reply again.
On Router A i have this config
ip route 0.0.0.0 0.0.0.0 192.168.50.3 so this is not static default route?
And 192.168.50.2 is next hop towards default route
Also from Router A
sh ip route shows
Gateway of last resort is 192.168.50.3 to network 0.0.0.0
S* 0.0.0.0/0 [1/0] via 192.168.50.3
BB#
D EX 192.168.6.2 [170/26137600] via 10.1.24.2, 00:55:10, Serial0/0
192.168.50.0/31 is subnetted, 1 subnets
C 192.168.50.2 is directly connected, FastEthernet0/0
Also Router A shows both the routes learned for 192.168.50.0
But you are absoutley correct as admin distance of directly connected is lower thats why it shows 192.168.50.2
in the topology table
Thanks
MAhesh
02-25-2012 02:38 PM
Hello Mahesh,
On Router A i have this config
ip route 0.0.0.0 0.0.0.0 192.168.50.3 so this is not static default route?
Yes, that is a static default route. However, in your show ip eigrp topology outputs, you have always pointed out the 192.168.50.2/31 network and called that a "static default route" which it isn't. Also note that the default route 0.0.0.0/0 never showed up in any of your show ip eigrp topology listings. That was quite confusing, as I was looking for the network 0.0.0.0/0 while you were only speaking about the network 192.168.50.2/31. That the IP address 192.168.50.3 happens to be the next hop towards the default route on Router A is largely unimportant.
And 192.168.50.2 is next hop towards default route
No, it is not. The next hop is, according both to the ip route command and the show ip route output, 192.168.50.3.
sh ip route shows
Gateway of last resort is 192.168.50.3 to network 0.0.0.0
S* 0.0.0.0/0 [1/0] via 192.168.50.3
BB#
D EX 192.168.6.2 [170/26137600] via 10.1.24.2, 00:55:10, Serial0/0
192.168.50.0/31 is subnetted, 1 subnets
C 192.168.50.2 is directly connected, FastEthernet0/0
Also Router A shows both the routes learned for 192.168.50.0
I apologize but which "both" routes do you mean here?
Best regards,
Peter
02-25-2012 02:48 PM
Hi Peter,
Sorry for the confusion
Router A
BB#sh ip eigrp topology
IP-EIGRP Topology Table for AS(90)/ID(172.30.8.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 0.0.0.0/0, 0 successors, FD is Inaccessible, tag is 1*************************************
via 10.1.24.2 (26137600/25625600), Serial0/0
So as per above we can say that Router A shows the default route right???????????
IT is inaccessible because it has higher Admin dustance then connected router right?
By both routes i mean 192.168.50.0.
Thanks
MAhesh
02-25-2012 03:04 PM
Hi Mahesh,
So as per above we can say that Router A shows the default route right???????????
Yes. Now the default route is being injected into EIGRP from another router and advertised to Router A.
IT is inaccessible because it has higher Admin dustance then connected router right?
Not entirely. It is inaccessible because it has a higher administrative distance than the static default route already present in your routing table in this case.
By both routes i mean 192.168.50.0.
The "192.168.50.0/31" is just a heading - a title - in the printout, not a real network. There is really only one 192.168.50.x network in your routing table - the 192.168.50.2/31. The title "192.168.50.0/31" means that all subnets of the once-classful network 192.168.50.0 are having the netmask of /31 and are listed below the title. Once again, the "192.168.50.0/31" in your routing table is not a network.
Best regards,
Peter
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: