change of IP address

Unanswered Question
Mar 19th, 2009

I have attached a diagram of my connection. What I want to do is to use router A ip address to router B. Router A is located remotely that no one can handle it onsite. Im just doing remote connection to both routers. How I can use router A ip adr to router B w/o sacrificing router A connection. I heard of second ip, but i havent tried this one. Pls. help

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Leo Laohoo Thu, 03/19/2009 - 03:18

To put a second IP Address, do this ...

int f0/0

ip address yada.yada.yada.yada blah.blah.blah.blah secondary

Then once that is done, telnet into the secondary address and remove the 1st IP Address.

Or you can create a loopback IP Address and telnet into that IP Address too.

suryakant.chavan Thu, 03/19/2009 - 04:57

we can't do as leolaohoo mention,

Router required to remove first secondary ip address before primary ip address.

korbenda11as Fri, 03/20/2009 - 00:27

is the loopback address which known via static route with next hop of 10.205.30.26 will also be unreachable once the ip addres of the interface was removed?

Leo Laohoo Thu, 03/19/2009 - 14:55

Gee ... Ok.

Presume you got this ...

int f 0/0

ip address 1.1.1.1 255.255.255.0

ip address 1.1.2.1 255.255.255.0 secondary

and you want to delete the first secondary, so you put another network there like "ip address 1.1.3.1 255.255.255.0", get out and telnet into the 1.1.3.1 and do a "no ip address 1.1.2.1 255.255.255.0 secondary".

Otherwise, create a loopback address and telnet into that and put the 1.1.3.1 secondary as well as remove the 1.1.2.1 address. Does this make sense to you?

korbenda11as Fri, 03/20/2009 - 00:26

but is the loopback address which is known only through the ip address of 10.205.30.26 will also be unreachable once the ip address of the interface was removed?

Giuseppe Larosa Thu, 03/19/2009 - 07:30

Hello Oliver,

a secondary ip address on a lan interface can fix this issue.

you still keep both the primary and secondary ip address.

to reach RA from another ip subnet a static route pointing to RB primary ip address can be used or a dynamic routing protocol like RIP or EIGRP to advertise the secondary ip address block

Hope to help

Giuseppe

rpfinneran Sat, 03/21/2009 - 23:46

Here is a generic process I have used many times to change the IP address of a remote router without loosing access. This works really well.

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PROCEDURE

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REMOTE - Enable telnet and ssh on VTY lines.

REMOTE - Remove any access class on VTY.

REMOTE - Schedule a reload for 10 minutes (In case something goes wrong, will restore access)

REMOTE - Add second static default route pointing out interface (ensure Unicast Reverse Path Forwarding isnt enabled on outbound interface first)

REMOTE - Remove any crypto map if applied. (Connectivity Lost)

HUB - Remove any crypto map from HUB if applied. (Connectivity Restored)

REMOTE - Change interface IP address. (Connectivity Lost)

HUB - Change interface iP address or VLAN assignment. (Connectivity restored)

REMOTE - Remove old static default route.

REMOTE - Add new static default using next hop instead of interface.

REMOTE - Remove static default that used interface.

REMOTE - Re-enable Unicast RPF if it was applied.

REMOTE - Re-apply crypto if used (Connectivity Lost)

HUB - Re-apply crypto if used (Connectivity Restored)

REMOTE - Add access class back to VTY.

REMOTE - Cancel Reload

REMOTE - Save Configurations.

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