Requiring the first as to be the neighbor as – Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) User Manual
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Multi-Service IronWare Routing Configuration Guide
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Requiring the first AS to be the neighbor AS
When selecting a route from among different sources (BGP4, OSPF, RIP, IS-IS, static routes, and so
on), the software compares the routes on the basis of the administrative distance for each route. If
the administrative distance of the paths is lower than the administrative distance of paths from
other sources (such as static IP routes, RIP, or OSPF), the BGP4 paths are installed in the IP route
table.
The default administrative distances on the device are:
•
Directly connected – 0 (this value is not configurable)
•
Static – 1 is the default and applies to all static routes, including default routes. This can be
assigned a different value.
•
EBGP – 20
•
OSPF – 110
•
IS-IS – 115
•
RIP – 120
•
IBGP – 200
•
Local BGP4 – 200
•
Unknown – 255 (the device will not use this route)
Lower administrative distances are preferred over higher distances. For example, if the device
receives routes for the same network from OSPF and from RIP, the device will prefer the OSPF route
by default. The administrative distances are configured in different places in the software. The
device re-advertises a learned best BGP4 route to neighbors by default, regardless of whether the
administrative distance for the route is lower than the administrative distances of other routes from
different route sources to the same destination:
•
To change the EBGP, IBGP, and Local BGP4 default administrative distances, refer to the
instructions in this section.
•
To change the default administrative distance for OSPF, RIP, IS-IS, refer to
To change the default administrative distances for EBGP, IBGP, and Local BGP4, enter a command
such as the following.
Brocade(config-bgp)# distance 200 200 200
Syntax: [no] distance external-distance internal-distance local-distance
The external-distance sets the EBGP distance and can be a value from 1 – 255.
The internal-distance sets the IBGP distance and can be a value from 1 – 255.
The local-distance sets the Local BGP4 distance and can be a value from 1 – 255.
Requiring the first AS to be the neighbor AS
By default, a device does not require the first AS listed in the AS_SEQUENCE field of an AS path
update message from EBGP neighbors to be the AS of the neighbor that sent the update. However,
you can enable the device to have this requirement. You can enable this requirement globally for
the device, or for a specific neighbor or peer group. This section describes how to enable this
requirement.