IBM 9077 Putting grifconfig.conf Additions into Effect, Change Profile Settings, Run dev1config

Default MTUs for framing protocols are:

•Frame Relay: 4352 bytes

•HDLC: 4352 bytes

•Point-to-Point Protocol: 1496 bytes

MTU discovery facility

MTU sizes are generally selected at the host end of the route. This is accomplished by turning on the host’s MTU discovery facility and allowing the host to send packets. The MTU discovery facility operates by default on the SP Switch Router. AIX4.3.1 provides MTU discovery; however, you have to enable it with the /etc/no command.

In effect, the discovery facility tells the router not to fragment, but instead to advise the host when the packet size is larger than the given path can handle. This allows the host to discover the largest packet that the most restrictive of the media components within the same path can handle. Once "discovered", the host then sends only packets in sizes matching the reported maximum, and so packets are not fragmented.

3.10.3 Putting grifconfig.conf Additions into Effect

Additions made to /etc/grifconfig.conf after first-time installation take effect only after the file is reloaded and the media card reset.

Use the grreset command to reset each configured SP Switch Router Adapter card by specifying the slot number where each card is installed, as follows:

grreset <card_slot_number>

3.11 Step 3. Change Profile Settings

As mentioned, this step is optional and explained in detail in GRF 400/1600 Configuration Guide 1.4, GA22-7366. The SP Switch Router will work happily with the default settings shipped with the system and there really is no need to change anything at this time.

3.12 Step 4. Run dev1config

If you followed the advice in Section 3.10.1, “Method 1: Use SP SNMP Manager - Recommended” on page 89, running the command dev1config should be all that needs to be done.

Installation and Configuration 95