Requiring the first as to be the neighbor as – Brocade TurboIron 24X Series Configuration Guide User Manual
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Brocade TurboIron 24X Series Configuration Guide
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Optional configuration tasks
Lower administrative distances are preferred over higher distances. For example, if the router
receives routes for the same network from OSPF and from RIP, the router will prefer the OSPF route
by default. The administrative distances are configured in different places in the software. The
Layer 3 Switch re-advertises a learned best BGP4 route to neighbors by default, regardless of
whether the route administrative distance is lower than other routes from different route sources to
the same destination.
•
To change the EBGP, IBGP, and Local BGP default administrative distances, see the
instructions in this section.
•
To change the default administrative distance for OSPF, refer to
•
To change the default administrative distance for RIP, refer to
•
To change the default administrative distance for static routes, refer to
You can change the default EBGP, IBGP, and Local BGP administrative distances using either of the
following methods.
To change the default administrative distances for EBGP, IBGP, and Local BGP, enter a command
such as the following.
TurboIron(config-bgp-router)#distance 180 160 40
Syntax: 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 BGP distance and can be a value from 1 – 255.
Requiring the first AS to be the neighbor AS
By default, the device does not require the first AS listed in the AS_SEQUENCE field of an AS path
Update from an EBGP neighbor to be the AS that the neighbor who sent the Update is in. You can
enable the device for this requirement.
When you enable the device to require the AS that an EBGP neighbor is in to be the same as the
first AS in the AS_SEQUENCE field of an Update from the neighbor, the device accepts the Update
only if the ASs match. If the ASs do not match, the device sends a Notification message to the
neighbor and closes the session. The requirement applies to all Updates received from EBGP
neighbors.
To enable this feature, enter the following command at the BGP configuration level of the CLI.
TurboIron(config-bgp-router)#enforce-first-as
Syntax: [no] enforce-first-as
Disabling or re-enabling comparison of the AS-Path length
AS-Path comparison is Step 5 in the algorithm BGP4 uses to select the next path for a route.
Comparison of the AS-Path length is enabled by default. To disable it, enter the following command
at the BGP configuration level of the CLI.
TurboIron(config-bgp-router)#as-path-ignore