Cheatsheet: Difference between revisions

* Route Selection Criteria

<center>

! Attribute !! Which is better !! Type

|Next Hop reachable || Route cannot be used if next hop is unreachable || Well-known Mandatory

|Weight || Bigger; value local to the router; Cisco proprietary; default is 0 for all routes not originated by local router ||

|Local Preference || Bigger; used within AS and exchanged bw iBGP routers; default is 100 || Well-known discretionary

|Locally Injected (Originate) || Prefer path local router originated; Locally injected > iBGP/eBGP learned; In BGP table it will hv next hop 0.0.0.0 ||

|AS Path Length || Smaller; e.g: AS path 1 2 3 is preferred over AS path 1 2 3 4 5 || Well-known Mandatory

|Origin || Prefer IGP(advertised by network cmd - i) > EGP > INCOMPLETE - '?'(reditributed) || Well-known Mandatory

|MED(Metric) || Smaller; used to advertise to neighbors how they should enter your AS; propagated to all routers within the neighbor AS but not passed along any other AS || Optional non-transitive

|Neighbor Type || Prefer eBGP over iBGP ||

|IGP Metric to Next Hop || Smaller; Prefer the path within the AS with the lowest IGP metric to the BGP next hop ||

|-

|Oldest path || Prefer the path that we received first ||

|-

|Router ID || Prefer the path with the lowest BGP neighbor router ID (Manually conf > Highest Loopback IP address > Highest Interface IP address) ||

|-

|Neighbor IP address || Prefer the path with the lowest neighbor IP address ||

</center>