Specifying A Maximum As Path Length - Brocade Communications Systems FastIron SX 800 Configuration Manual

Specifying a maximum AS path length

not enabled, the status field displays only the default letter "E", as displayed for BGP4 route 10.12.0.0/24. The letter "B" or "b" is missing
from the Status field.
NOTE
The description of the status "b: NOT-INSTALLED-BEST" has changed. The status description for "b: NOT-INSTALLED-
BEST" is now: The routes received from the neighbor are the best BGP4 routes to their destinations, but were nonetheless not
installed in the IP route table due to the rib-route-limit option (or RTM route table size limit), and the always-propagate option
to allow the propagating of those best BGP routes.
NOTE
Traffic loss on a BGP4 route occurs when a device is advertising preferred BGP4 routes not installed in the RTM as part of the
forwarding path.
Because the BGP4 route 10.12.0.0/24 is not considered as the best BGP4 route, the route is not advertised to other BGP4 neighbors.
device(config-bgp)# show ip bgp route 10.12.0.0/24
Number of BGP Routes matching display condition : 1
Status A:AGGREGATE B:BEST b:NOT-INSTALLED-BEST C:CONFED_EBGP D:DAMPED
E:EBGP H:HISTORY I:IBGP L:LOCAL M:MULTIPATH m:NOT-INSTALLED-MULTIPATH
S:SUPPRESSED F:FILTERED s:STALE
Prefix
1 10.12.0.0/24
AS_PATH: 48 1994 65148 21948 6461 1239 4837 4808 17431 18245
Last update to IP routing table: 0h16m2s
No path is selected as BEST route
Syntax: show ip bgp route ip-address/prefix
After enabling the always-propagate command, the BGP4 route is now considered the best BGP4 route, even though the route is not
installed in the RTM. Because the rib-route-limit command was configured to allow for only 300,000 routes in the RTM some preferred
BGP4 routes are not installed in the RTM, and are not advertised to other BGP4 neighbors. By enabling the always-propagate
command, the device is now able to advertise those preferred BGP4 routes to other BGP4 neighbors. In the following example, the
Status field displays "bE" indicating that the route is now considered the best BGP4 route for forwarding and will be advertised to other
BGP4 neighbors.
device(config-bgp)# show ip bgp route 10.12.0.0/24
Number of BGP Routes matching display condition : 1
Status A:AGGREGATE B:BEST b:NOT-INSTALLED-BEST C:CONFED_EBGP D:DAMPED
E:EBGP H:HISTORY I:IBGP L:LOCAL M:MULTIPATH m:NOT-INSTALLED-MULTIPATH
S:SUPPRESSED F:FILTERED s:STALE
Prefix
1 10.12.0.0/24
AS_PATH: 48 1994 65148 21948 6461 1239 4837 4808 17431 18245
Last update to IP routing table: 0h12m53s
Route is to be sent to 1 peers:
10.0.0.14(6)
For an explanation of the fields displayed in the output of the show ip bgp route command, refer to
route on page 455.

Specifying a maximum AS path length

You can use the maxas-limit in command to configure a device running BGP4 to discard routes that exceed a specified AS path limit.
This limit can be configured globally, for peer groups, and for BGP neighbors.
432
Next Hop MED
10.100.100.4
Next Hop MED
10.100.100.4
LocPrf Weight Status
100 0 E
LocPrf Weight Status
100 0 bE
Displaying information for a specific
FastIron Ethernet Switch Layer 3 Routing
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