Changing The Router Id - Dell PowerConnect B-RX Configuration Manual

7

Changing the router ID

Globally changing the IP MTU
To globally enable jumbo support on all ports, enter commands such as the following.
BigIron RX(config)# ip mtu 5000
BigIron RX(config)# write memory
Syntax: [no] ip mtu <bytes>
The <bytes> parameter specifies the maximum number of bytes an Ethernet frame can have in
order to be forwarded on a port. Enter 64 – 9212, but this value must be 18 bytes less than the
value of the global maximum frame size.
NOTE
The BigIron RX will always use 22 Bytes less than the configured MTU in order to compensate for the
4Bytes required for VLAN tags. This is so if a packet is forwarded on both a tagged and untagged
link within a VLAN, it will get through.
Changing the maximum transmission unit on an individual interface
By default, the maximum IP MTU sizes are as follows:
•
•
NOTE
The IP MTU configured at the physical interface level takes precedence over the IP MTU configured
at the global level for that physical interface.
To change the IP MTU for interface 1/5 to 1000, enter the following commands.
BigIron RX(config)# int e 1/5
BigIron RX(config-if-e10000-5)# ip mtu 1000
Syntax: [no] ip mtu <bytes>
The <bytes> parameter specifies the IP MTU. Ethernet II packets can hold IP packets from 572 –
1500 bytes long. Ethernet SNAP packets can hold IP packets from 572 – 1492 bytes long.
However, the value of IP MTU on an interface cannot exceed the configured value of IP MTU for an
interface, minus 18 bytes. The default IP MTU for Ethernet II packets is 1500. The default IP MTU
for SNAP packets is 1492.
Changing the router ID
In most configurations, a device has multiple IP addresses, usually configured on different
interfaces. As a result, a device's identity to other devices varies depending on the interface to
which the other device is attached. Some routing protocols, including OSPF and BGP4, identify a
device by just one of the IP addresses configured on the device, regardless of the interfaces that
connect the devices. This IP address is the router ID.
NOTE
RIP does not use the router ID.
182
1500 bytes – The maximum for Ethernet II encapsulation
1492 bytes – The maximum for SNAP encapsulation
BigIron RX Series Configuration Guide
53-1002253-01