Limitations of IP un-numbered

[rsmadhava]

I have a few questions :

I have a router with 2 serial interface and one ethernet port. Both serial ports are connected to different networks.

1. Is it possible to use IP un-number to both serial interface ?

2. The ethernet port has an IP number which i use to un-number s0. I also have an alias IP number to same ethernet interface and can I use that aliased IP number to create an un-numbered interface on s1 ?

3. Is it possible to have two default static routes, one pointing to s0 and other pointing to s1 ? If yes, which port is normally used as default gateway and in case of failure of that link, will another port automatically take the traffic ? Or will it work as load sharing ??

 

[BuckWeet]

Here's a big downfall to IP Unnumbered that you should be aware of..

Say you're getting the IP from the ethernet...

On the remote router, the ethernet gets unplugged, shutdown, or whatever. Well since that interface is down, you won't have an address applied to the serial interface, so you have no remote access to even being to troubleshoot the issue. This reason alone is why I refused to use this.


BuckWeet

 

[tschouten]

BuckWeet,

Can't you get around that problem by using a loopback interface for the addressing? (That is if you are using OSPF).

 

[BuckWeet]

Sure you could, but it doesn't make sense to create a loopback interface when you don't need it just for addressing.. if you were running some kind of routing protocol that needs it, thats a diff story.. also there are some limitations that I can't remeber fully, but the networks have to be in the same class I think. I can't really remember. Oh well..


BuckWeet

 

[jimmyzz]

The only real advantage of IP unnumbered is that is saves on IP addresses, which is not a huge saving if you're using a private addressing scheme. The only real disadvantage is that the serial interface connectivity can not be tested remotely because the IP for it is not available.

JimmyZ

 

[wybnormal]

A disadvantage is that with an unnumbered interface like S0 for an example, you can not telnet to that interface.. no ip, no telnet. That can be a problem when trying to troubleshoot a network link. I have times where I needed to telnet to the serial interface and then jump from there.

Just a thought.

MikeS


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Sun Tzu

 

[rsmadhava]

I have given 192.168.10.1 to ethernet port and 203.100.5.1 as secondary address to that port. Can I use this secondary address (alias IP) to unnumber a serial interface ?

 

[pbxphoneman]

hmmm..even if have a static address (eth) on both my ptp T1 routers I will lose the ability to Telnet into the remote router if I'm using an unnumbered WAN Link?I would have to have a PC up on the interface in order to Telnet into the router? I don't like not having remote access to it.

 

[StarTAC]

i use loopback interfaces, even on active serial interfaces, and they work fine.. i can ping, telnet, e.t.c

interestingly, i have not experienced some of the documented limitations on the cisco site..