Cheatsheet: Difference between revisions

! Attribute !! Which is better !! Direction

|Next Hop reachable || Route cannot be used if next hop is unreachable ||

|Weight || Bigger ||

|Local Preference || Bigger ||

|Locally Injected || Locally injected is better than iBGP/eBGP learned ||

|AS Path Length || Smaller ||

|Origin || Prefer I over E & E over Unknown ||

|MED || Smaller ||

|Neighbor Type || Prefer eBGP over iBGP ||

|IGP Metric to Next Hop || Smaller ||

* Directions

'''Aspath prepend:''' Applied outwardly.

Impacts incoming path.

Shorter the as-path length higher the preference

As-path prepend is the way to add AS number to the list of subnet u want to advertise.

This is a way to route poisoning.

Tell the outside world not to follow the path.

'''Local preference:''' Applied while the traffic coming inside.

Impacts traffic while going out.

Non transitive.

Propagates within the same as-path.

Higher the local preference value higher the preference

'''MED:''' Multiexitdescriptor

When your router has connection with two other routers with same AS.

Let's say you have 2 subnets behind your router.

You can use MED value to mention which networks should be accessed through which links.

It is advertised outwards.

Impacts the incoming traffic.

Semi transitive.

Propagates to one AS.

Lower the MED value higher the preference.

MED should be used carefully as it reduces network resiliency.