Brocade TurboIron 24X Series Configuration Guide - Manual (Page 737)

Brocade TurboIron 24X Series Configuration Guide 703
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Filtering
TurboIron(config-bgp-router)#address-filter 1 deny 10.157.0.0 255.255.0.0
Syntax: address-filter <num> permit | deny <ip-addr> <wildcard> <mask> <wildcard>
The <num> parameter is the filter number.
The permit | deny parameter indicates the action the Layer 3 Switch takes if the filter match is true.
• If you specify permit, the Layer 3 Switch permits the route into the BGP4 table if the filter
match is true.
• If you specify deny, the Layer 3 Switch denies the route from entering the BGP4 table if the
filter match is true.
NOTE
Once you define a filter, the default action for addresses that do not match a filter is “deny”. To
change the default action to “permit”, configure the last filter as “permit any any”.
The <ip-addr> parameter specifies the IP address. If you want the filter to match on all addresses,
enter any.
The <wildcard> parameter specifies the portion of the IP address to match against. The <wildcard>
is in dotted-decimal notation (IP address format). It is a four-part value, where each part is 8 bits
(one byte) separated by dots, and each bit is a one or a zero. Each part is a number ranging from 0
to 255, for example 0.0.0.255. Zeros in the mask mean the packet source address must match the
<source-ip>. Ones mean any value matches. For example, the
<ip-addr> and <wildcard> values 10.157.22.26 0.0.0.255 mean that all hosts in the Class C
subnet 10.157.22.x match the policy.
If you prefer to specify the wildcard (mask value) in Classless Interdomain Routing (CIDR) format,
you can enter a forward slash after the IP address, then enter the number of significant bits in the
mask. For example, you can enter the CIDR equivalent of “10.157.22.26 0.0.0.255” as
“10.157.22.26/24”. The CLI automatically converts the CIDR number into the appropriate mask
(where zeros instead of ones are the significant bits) and changes the non-significant portion of the
IP address into zeros. For example, if you specify 10.157.22.26/24 or 10.157.22.26 0.0.0.255,
then save the changes to the startup-config file, the value appears as 10.157.22.0/24 (if you have
enabled display of subnet lengths) or 10.157.22.0 0.0.0.255 in the startup-config file.
If you enable the software to display IP subnet masks in CIDR format, the mask is saved in the file
in “/<mask-bits>” format. To enable the software to display the CIDR masks, enter the ip
show-subnet-length command at the global CONFIG level of the CLI. You can use the CIDR format to
configure the filter regardless of whether the software is configured to display the masks in CIDR
format.
The <mask> parameter specifies the network mask. If you want the filter to match on all
destination addresses, enter any. The wildcard works the same as described above.
Filtering AS-paths
You can filter updates received from BGP4 neighbors based on the contents of the AS-path list
accompanying the updates. For example, if you want to deny routes that have the AS 10.4.3.2 in
the AS-path from entering the BGP4 route table, you can define a filter to deny such routes.
The Layer 3 Switch provides the following methods for filtering on AS-path information:
• AS-path filters
• AS-path ACLs