If an IPv4 packet is larger than the IP MTU allowed by the frame, the device fragments the IP packet into multiple parts that fit into frames, and sends the parts of the fragmented IP packet in separate frames. The device that receives the multiple fragments of the IP packet reassembles these fragments into the original packet. The default IPv4 MTU is 1500 bytes for Ethernet II packets.
There are limitations on IP MTU. The following table lists the IP MTU Profile Counts for various devices.
| Platform | L3 IP MTU Profile Count | Description |
|---|---|---|
| SLX 9150/SLX 9250/Extreme 8520/Extreme 8720 | 7915 | A maximum of 7915 entries can be configured based on MTU range 1280-9194, (both inclusive). MTU value is stored on the hardware on a per interface basis. |
| SLX 9540/SLX 9640 | 3 | 1 Default IP MTU (1500), 2 user-defined MTU profiles |
| SLX 9740/Extreme 8820 | 7 | 1 Default IP MTU (1500), 5 user-defined MTU profiles, 1 GRE Tunnel (1476) |
%Error: Maximum limit of allowed different IP MTUs reached.
You can increase the IP MTU to reduce packet fragmentation. However, IP MTU cannot be higher than the maximum frame size, minus 18. For more information, see IPv4 MTU and Maximum Frame Size.
The device supports hardware forwarding for unicast jumbo packets that are received on a port that supports the frame's IP MTU size and are forwarded to another port that also supports the frame's IP MTU size.
Note
For multicast data traffic, frames are not fragmented and the IP MTU setting is ignored.