Setup Guide
maximum-paths {ebgp | ibgp} number
Congure the following parameters:
– ebgp: Enable multipath support for external BGP routes.
– ibgp: Enable multipath support for internal BGP routes.
–
number: Maximum number of parallel paths. The range is from 2 to 64.
Example conguration for enabling multipath
DellEMC# configure terminal
DellEMC(conf)# router bgp 400
DellEMC(conf-router_bgp)# maximum-paths ibgp 5
DellEMC(conf-router_bgp)# exit
In the above example conguration, the maximum number of parallel internal BGP routes is set to 5, so that only 5 routes can be installed in
a routing table.
The show ip bgp network command includes multipath information for that network.
Route Reectors
Route reectors reorganize the iBGP core into a hierarchy and allow some route advertisement rules.
NOTE: Do not use route reectors (RRs) in the forwarding path. In iBGP, hierarchal RRs maintaining forwarding plane RRs could
create routing loops.
Route reection divides iBGP peers into two groups: client peers and nonclient peers. A route reector and its client peers form a route
reection cluster. Because BGP speakers announce only the best route for a given prex, route reector rules are applied after the router
makes its best path decision.
• If a route was received from a nonclient peer, reect the route to all client peers.
• If the route was received from a client peer, reect the route to all nonclient and all client peers.
To illustrate how these rules aect routing, refer to the following illustration and the following steps. Routers B, C, D, E, and G are members
of the same AS (AS100). These routers are also in the same Route Reection Cluster, where Router D is the Route Reector. Router E and
H are client peers of Router D; Routers B and C and nonclient peers of Router D.
Figure 25. BGP Router Rules
1 Router B receives an advertisement from Router A through eBGP. Because the route is learned through eBGP, Router B advertises it
to all its iBGP peers: Routers C and D.
2 Router C receives the advertisement but does not advertise it to any peer because its only other peer is Router D, an iBGP peer, and
Router D has already learned it through iBGP from Router B.
3 Router D does not advertise the route to Router C because Router C is a nonclient peer and the route advertisement came from
Router B who is also a nonclient peer.
4 Router D does reect the advertisement to Routers E and G because they are client peers of Router D.
5 Routers E and G then advertise this iBGP learned route to their eBGP peers Routers F and H.
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Border Gateway Protocol (BGP)