Service Manual

Table 8. BGP Default Values (continued)
Item Default
Graceful Restart feature Disabled
Local preference 100
MED 0
Route Flap Damping Parameters
half-life = 15 minutes
reuse = 750
suppress = 2000
max-suppress-time = 60 minutes
Distance
external distance = 20
internal distance = 200
local distance = 200
Timers
keepalive = 60 seconds
holdtime = 180 seconds
Add-path Disabled
Implement BGP with Dell EMC Networking OS
The following sections describe how to implement BGP on Dell EMC Networking OS.
Additional Path (Add-Path) Support
The add-path feature reduces convergence times by advertising multiple paths to its peers for the same address prefix without
replacing existing paths with new ones. By default, a BGP speaker advertises only the best path to its peers for a given address
prefix. If the best path becomes unavailable, the BGP speaker withdraws its path from its local RIB and recalculates a new best
path. This situation requires both IGP and BGP convergence and can be a lengthy process. BGP add-path also helps switchover
to the next new best path when the current best path is unavailable.
Advertise IGP Cost as MED for Redistributed Routes
When using multipath connectivity to an external AS, you can advertise the MED value selectively to each peer for redistributed
routes. For some peers you can set the internal/IGP cost as the MED while setting others to a constant pre-defined metric as
MED value.
Use the set metric-type internal command in a route-map to advertise the IGP cost as the MED to outbound EBGP
peers when redistributing routes. The configured set metric value overwrites the default IGP cost.
By using the redistribute command with the route-map command, you can specify whether a peer advertises the
standard MED or uses the IGP cost as the MED.
When configuring this functionality:
● If the redistribute command does not have metric configured and the BGP peer outbound route-map does have
metric-type internal configured, BGP advertises the IGP cost as MED.
● If the redistribute command has metric configured (route-map set metric or redistribute route-type
metric) and the BGP peer outbound route-map has metric-type internal configured, BGP advertises the metric
configured in the redistribute command as MED.
● If BGP peer outbound route-map has metric configured, all other metrics are overwritten by this configuration.
NOTE:
When redistributing static, connected, or OSPF routes, there is no metric option. Simply assign the appropriate
route-map to the redistributed route.
The following table lists some examples of these rules.
Border Gateway Protocol (BGP)
181