Last Updated on July 31, 2021 by Admin 1
Company A recently acquired Company B and the network infrastructures are being merged. Both organizations used non-overlapping globally unique network addressing but different Interior Gateway Protocols (IGPs). Initially, multiple WAN links will connect the two organizations. Company A will maintain its core routing protocol, and Company B’s routing protocol will be the edge routing protocol. Two-way redistribution will be used to ensure full network routing capability.What additional routing configuration should be performed to prevent routing loops and suboptimal routing?
- Manually configure static routes.
- Manually configure default routes.
- Manually adjust the administrative distances.
- Manually adjust the local preference attribute.
When routes are being redistributed from the core into the edge and from the edge into the core, the administrative distance (AD) associated with external routes should be modified. This lessens the possibility of sub-optimal routing when multiple routing protocols advertise different paths to the same network. The AD associated with the externally advertised routes should be higher than the internal IGP’s AD. To change the AD for an entire routing protocol, use the distance command. An example and the command syntax are shown below:
router(config)#router rip router(config-router)#distance 125
The complete syntax of the distance command is:
distance weight [address mask [ access-list-number | name]
The weight parameter is the AD, which can be a number from 10 to 255. Note that distances 0 through 9 are reserved for system use.
To change only the AD for selected networks, use an access list with the distance command as shown below:
router(config)# access-list 5 permit 10.0.0.0 255.0.0.0 router(config)# access-list 5 permit 126.96.36.199 255.0.0.0 router(config)# access-list 5 permit 188.8.131.52 255.0.0.0 router(config)# router rip router(config-router)# distance 220 0.0.0.0 255.255.255.255 5
The 0.0.0.0 255.255.255.255 portion included with the distance command could hold an address/mask combination for a single address, but it is more common to use an access list.
Layer 3 Technologies
Configure and verify redistribution between any routing protocols or routing sources