OSPF support for Secondary IP

[tj6512]

Hello,

Currrently we are using public IP as our LAN IP and we are planning to migrate our existing public IP LAN to private IP LAN. On top of that, we will assign part of these private IP reserved for static IP user, and part of these private IP assigned for DHCP clients (same IP subnet). The DHCP servers will be located at HQ. On the routers we will configure ip helper to redirect the DHCP message. We have a dedicated leased line connected between HQ and regional offices. These WAN are running on OSPF.

Question:

1)Can we configure a secondary IP address on the regional router's ethernet port (we only have a single ethernet port for regional office) so that the current public IP LAN and private IP LAN can co-exist? Because we can only migrate the public IP address by department. Once all the public IP client has been migrated to private IP, then we will configure the regional router's ethernet port as a single private IP and remove the public IP address.

2) Would there be any potential problem on the OSPF learning/routing for the secondary LAN IP?

Thank you for your prompt reply.

[stuart.l2]

No problem on the interface wth secondary addresses.

OSPF dosen't support the use of secondary addressing .

Perhaps you can redistribute a static/connected routes into you OSPF process

[tj6512]

Hello,

Thank you for your prompt reply. That means i can still use the secondary IP during the migration period. However, i will need to configure a static route for the secondary IP address. If the primary link down, the routing for the secondary IP will not automatically routed to the backup link, unless i specific a secondary route for the secondary IP to route on backup link?

Thank you.

[lldygowski]

OSPF DOES support secondary addreses, but OSPF adjacencies will only be formed over primary networks and not the secondary networks. If you add the appropriate network statement in the router ospf config for the secondary addresses they will be advertised in OSPF. The link below may help provide more information:

http://www.cisco.com/en/US/customer/tech/tk648/tk365/technologies_tech_note09186a0080094050.shtml

[linxiang]

yes, tj6512 is right. if you add the private network statement in the OSPF config for the secondary address, there is no problem for you to implement you plan, but you must be care for what you wildcard use.

[nsabnis]

dear u can give eth int a sce ip address.

sysntex--ip address sec

remember one thing when u give 2 address to an ethernet and u r using any routing protocol. routing update will only sent by primary eth address.