Take the 2-minute tour ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.

May sound like a stupid question but just wanted to make sure. Does every serial connection need to have its own IP address.

Router 1:
Serial 0/0/0 IP address 172.10.80.193/30
Serial 0/1/0 IP address 172.10.80.197/30

Router 2:
Serial 0/0/0 IP address 172.10.80.194/30

Router 3:
Serial 0/1/0 IP address 172.10.80.198/30
share|improve this question
    
Every interface that expects to route IP generally needs an IP address. –  Joseph Kern May 7 '12 at 0:06

2 Answers 2

up vote 4 down vote accepted

No. A point-to-point link does not have to have its own IP address. Point-to-point links can be unnumbered.

You can, for example, have one router with an IP address of 192.168.120.3 on the 192.168.120.0/24 LAN and another router with an IP address of 192.168.121.9 on the 192.168.121.0/24 LAN. They can have a serial link with one end numbered 192.168.120.3 and the other 192.168.121.9 without needing additional IP addresses just for the link.

Logically, to enable IP on interface S0, you would need to configure a unique IP address on it. However, it is also possible to enable IP on the Serial interface and bring it up without assigning a unique IP address to it. This is done by borrowing an IP address already configured on one of the router's other interfaces. To do this, the ip unnumbered interface mode command is used as shown below. -- Understanding and Configuring the ip unnumbered Command

share|improve this answer
    
Just to corroborate: I have run many Serial point-to-point connections passing IP that didn't have IP addresses. –  wfaulk May 7 '12 at 0:33

Every interface on an IP router needs its own IP address, yes.

However, if you're using IPv6 the cool thing is that it can be the same IPv6 address (link-local address).

share|improve this answer
    
ok just in our spec we have been given the ip on the serial connection from the isp router to isp and the internet gateway address 20.0.0.1, got my network working just not sure how to connect it all up to the isp –  Melevin Mandana May 6 '12 at 19:34
1  
This is just false. Point-to-point links do not need their own IP address. –  David Schwartz May 6 '12 at 23:41
    
… I learned something! –  MikeyB May 7 '12 at 13:46

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.