From: Gustavo Novais (gustavo.novais@novabase.pt)
Date: Fri Jan 13 2006 - 09:01:17 GMT-3
Hi Top.
Unfortunately I have found no link explaining why that is like that.
Probably it may be a safeguard, to avoid the case that I used as an
example. (changing routes AD indiscriminately whether they are external
or internal).
If it would be possible then, by default, we would probably mess up
while redistributing things, so someone chose to implement this
behaviour. If any of the Guru's would like to contribute...
I have no link that explains this behaviour, I observed this while doing
some labs.
Posted on GS and had a nice discussion with Chris Lewis regarding this
subject. We've also discussed distance command applied to OSPF and ISIS.
Just to add to the discussion the topology point of view of both routes
internal and external:
R2#sh ip eigrp topology 12.12.33.0 255.255.255.0
IP-EIGRP (AS 10): Topology entry for 12.12.33.0/24
State is Passive, Query origin flag is 1, 1 Successor(s), FD is
2560002816
Routing Descriptor Blocks:
192.168.23.3 (FastEthernet0/1), from 192.168.23.3, Send flag is 0x0
Composite metric is (2560002816/2560000256), Route is External
Vector metric:
Minimum bandwidth is 1 Kbit
Total delay is 110 microseconds
Reliability is 1/255
Load is 1/255
Minimum MTU is 1
Hop count is 1
External data:
Originating router is 12.12.3.3
AS number of route is 0
External protocol is Connected, external metric is 0
Administrator tag is 0 (0x00000000)
R2#sh ip eigrp topology 12.12.3.0 255.255.255.0
IP-EIGRP (AS 10): Topology entry for 12.12.3.0/24
State is Passive, Query origin flag is 1, 1 Successor(s), FD is 156160
Routing Descriptor Blocks:
192.168.23.3 (FastEthernet0/1), from 192.168.23.3, Send flag is 0x0
Composite metric is (156160/128256), Route is Internal
Vector metric:
Minimum bandwidth is 100000 Kbit
Total delay is 5100 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 1
R2#
Some other thing that I found:
EIGRP does not prefer internal vs external (contrary to OSPF). If
changing AD of internal routes to 170, lower metric will be preferred
despite the fact that they might be external. This may add something to
the discussion of the distance command. As OSPF has (by default same
metric for internal and external routes) mechanisms to distinguish and
prefer IA->E1->E2, EIGRP apparently does not. So the protocol prefers
internal just by the fact that they have less AD.
Just to illustrate ( I injected same route on EIGRP from other path, and
changed AD of internal routes):
R2#sh ip eigrp topolog 12.12.33.0 255.255.255.0
IP-EIGRP (AS 10): Topology entry for 12.12.33.0/24
State is Passive, Query origin flag is 1, 1 Successor(s), FD is 30720
Routing Descriptor Blocks:
192.168.23.3 (FastEthernet0/1), from 192.168.23.3, Send flag is 0x0
Composite metric is (30720/28160), Route is External
Vector metric:
Minimum bandwidth is 100000 Kbit
Total delay is 200 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 1
External data:
Originating router is 12.12.3.3
AS number of route is 0
External protocol is Connected, external metric is 0
Administrator tag is 0 (0x00000000)
192.168.23.1 (FastEthernet0/1), from 192.168.23.1, Send flag is 0x0
Composite metric is (156160/128256), Route is Internal
Vector metric:
Minimum bandwidth is 100000 Kbit
Total delay is 5100 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 1
R2#
R2#sh ip route eigrp
170.170.0.0/24 is subnetted, 1 subnets
D EX 170.170.170.0 [170/30720] via 192.168.23.3, 00:00:48,
FastEthernet0/1
12.0.0.0/24 is subnetted, 5 subnets
D 12.12.3.0 [170/156160] via 192.168.23.3, 00:03:09,
FastEthernet0/1
D EX 12.12.33.0 [170/30720] via 192.168.23.3, 00:00:48,
FastEthernet0/1
R2#
As you can see, I have on my topology internal route 12.12.33.0 via
192.168.23.1 but EIGRP prefers the external route with lower metric.
As I already said, I have no document that states explicitly why things
are as we can observe while playing with EIGRP, so this may reduce
itself to an academic discussion.
HTH
Gustavo Novais
________________________________
From: topgun topgun [mailto:topgunrs1@yahoo.com.sg]
Sent: sexta-feira, 13 de Janeiro de 2006 2:04
To: Gustavo Novais; n
Cc: ccielab@groupstudy.com
Subject: RE: [SPAM] - Re: Distance command for eigrp - Sending mail
server found on dnsbl.njabl.org
Hi Gustavo,
Do you have any link to recommend that explain why external eigrp routes
will not work for this distance command in eigrp protocol?
Thanks in advance.
Top
Gustavo Novais <gustavo.novais@novabase.pt> wrote:
Hi,
You may use distance to change AD of specific EIGRP internal
routes. You
may not use it to change AD of specific EIGRP external routes.
This
means that or you change the distance for all eigrp external
routes, or
you don't. :)
router eigrp 10
network 12.12.2.2 0.0.0.0
network 192.168.23.2 0.0.0.0
distance 100 192.168.23.3 0.0.0.0 ROUTES
no auto-summary
!
ip access-list standard ROUTES
permit 12.12.33.0 0.0.0.255
permit 12.12.3.0 0.0.0.255
on the example 12.12.33.0 is an external route on which I'm
trying to
set its distance to 100. I will not be able to.
R2#sh ip route eigrp
170.170.0.0/24 is subnetted, 1 subnets
D EX 170.170.170.0
[170/2560002816] via 192.168.23.3, 00:02:12, FastEthernet0/1
12.0.0.0/24 is subnetted, 5 subnets
D 12.12.3.0 [100/156160] via 192.168.23.3, 00:02:12,
FastEthernet0/1
D EX 12.12.33.0
[170/2560002816] via 192.168.23.3, 00:02:12, FastEthernet0/1
R2#
As you can see 12.12.3.0 which is internal gets its distance
changed to
100 but the external route 12.12.33.0 does not.
Hope this helps
Gustavo Novais
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
Behalf Of
n
Sent: quinta-feira, 12 de Janeiro de 2006 17:59
To: topgun topgun
Cc: ccielab@groupstudy.com
Subject: [SPAM] - Re: Distance command for eigrp - Sending mail
server
found on dnsbl.njabl.org
You can use the distance command to modify AD of various
protocols. Its
applied under the routing process. AFAIK that would apply to
routes
learned
by that router for that protocol or originating on that router.
http://www.cisco.com/warp/public/105/admin_distance.html
----- Original Message -----
From: "topgun topgun"
To:
Sent: Wednesday, January 11, 2006 5:36 PM
Subject: Distance command for eigrp
> Hi all,
>
> Have anyone try the distance command use in EIGRP?
> Can I use it to increase the AD of an EIGRP route coming in
from one
of
the router interface?
>
> Thanks,
>
> Top
>
>
>
> ---------------------------------
> Meet your soulmate!
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>
>
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