Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 61)

Disabling forwarding of IP source-routed packets
A source-routed packet specifies the exact router path for the packet. The packet specifies the path by
listing the IP addresses of the router interfaces through which the packet must pass on its way to the
destination. The Layer 3 switch supports both types of IP source routing:
• Strict source routing - requires the packet to pass through only the listed routers. If the Layer 3 switch
receives a strict source-routed packet but cannot reach the next hop interface specified by the
packet, the Layer 3 switch discards the packet and sends an ICMP Source-Route-Failure message to
the sender.
NOTE
The Layer 3 switch allows you to disable sending of the Source-Route-Failure messages.
• Loose source routing - requires that the packet pass through all of the listed routers but also allows
the packet to travel through other routers, which are not listed in the packet.
The Layer 3 switch forwards both types of source-routed packets by default. To disable the feature, use
either of the following methods. You cannot enable or disable strict or loose source routing separately.
To disable forwarding of IP source-routed packets, enter the no ip source-route command.
device(config)# no ip source-route
Syntax: [no] ip source-route
To re-enable forwarding of source-routed packets, enter the ip source-route command.
device(config)# ip source-route
Enabling support for zero-based IP subnet broadcasts
By default, the Layer 3 switch treats IP packets with all ones in the host portion of the address as IP
broadcast packets. For example, the Layer 3 switch treats IP packets with 10.157.22.255/24 as the
destination IP address as IP broadcast packets and forwards the packets to all IP hosts within the
10.157.22.x subnet (except the host that sent the broadcast packet to the Layer 3 switch).
Most IP hosts are configured to receive IP subnet broadcast packets with all ones in the host portion of
the address. However, some older IP hosts instead expect IP subnet broadcast packets that have all
zeros instead of all ones in the host portion of the address. To accommodate this type of host, you can
enable the Layer 3 switch to treat IP packets with all zeros in the host portion of the destination IP
address as broadcast packets.
NOTE
When you enable the Layer 3 switch for zero-based subnet broadcasts, the Layer 3 switch still treats IP
packets with all ones the host portion as IP subnet broadcasts too. Thus, the Layer 3 switch can be
configured to support all ones only (the default) or all ones and all zeroes.
NOTE
This feature applies only to IP subnet broadcasts, not to local network broadcasts. The local network
broadcast address is still expected to be all ones.
Disabling forwarding of IP source-routed packets
FastIron Ethernet Switch Layer 3 Routing Configuration Guide 61
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