Many a times, while working on dynamic Routing protocols (especially EIGRP) we often tend to get caught up on functional difference between Distribute List and Offset List. In discussions on various blogs, we get to understand that Distribute list functions to control the Routes which are advertised or received while Offset List function is to modify the advertised/received metric of Routes. Somewhere, one liners or definition of terms may not clearly give a view of the terms. Hence, let’s take a lab scenario to help practically understand the difference between both terms and how to implement them.
In the below scenario, we will take example of EIGRP Routing Protocol and with 2 Routers R1 and R2 connected Back to Back on FastEthernet port Fa0/0 on each end. Both have 3 Loopbacks interfaces of /32 each advertised over EIGRP.
CONFIGURING DISTRIBUTE LIST –
Hence , as Rightly said in the definition of “Distribute List” – It controls the Routes which are advertised or received. In the above scenario, distribute calls the Access list matching Subnet 22.214.171.124/32 controls i.e. stops its entry into R2 EIGRP table.
MOVING ON TOWARDS OFFSET LIST –
Now, Am sure we have more clarity of how Distribute List and Offset List differ and how to configure them.