Configuring the Maximum Packet Size

Configuring the maximum packet size allows the user to set a maximum IP packet size for packets that traverse an LSP without being fragmented. It can be configured for both primary and secondary paths.

To configure a maximum IP packet size for an LSP, complete the following steps.

Enable the device for configuration.
```
device# configure
```
Enable the MPLS router.
```
device(config)# router mpls
```
enable and configure the label switched path (LSP).
```
device(config-router-mpls)# lsp tunnel1
```
In this example, the LSP specified name is tunnel1.
Configure the IP packet maximum transmission unit size.
```
device(config-router-mpls-lsp-tunnel1)# ipmtu 1500
```
In this example, the packet-size variable specifies the maximum packet size in bytes for IP packets transiting the LSP without being fragmented.

Example

The following example configures a maximum IP packet size of 1500 bytes for LSP tunnel1.

device# configure terminal
device(config)# router mpls
device(config-router-mpls)# lsp tunnel1
device(config-router-mpls-lsp-tunnel1)# ipmtu 1500