Lucent Technologies 9077 16S - Manual (Page 57)

Configuring the SP Switch Router Adapter
Step 2. Assign IP addresses
SP Switch Router Adapter Guide - 1.4 Update 2 October 22, 1999 2-23
Argument field
This field is optional for SP Switch Router Adapter cards. The arguments field usually specifies
an MTU value different from the coded default value of 65520.
Default MTU values
The default MTUs for SP Switch Router media are:
SP Switch Router Adapter: 65520 bytes
HIPPI: 65280 bytes
FDDI: 4352 bytes
ATM OC-3c: 9180 bytes
ATM OC-12c: 9180 bytes
10/100Base-T: 1500 bytes
The default MTUs for these framing protocols are:
Frame Relay: 4352 bytes
HDLC: 4352 bytes
Point-to-Point Protocol: 1496 bytes
MTU discovery facility
Maximum Transmission Unit (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.
In effect, the discovery facility tells the router not to fragment, but 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 which 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 packets are not fragmented.
Putting grifconfig.conf additions into effect
Additions made to /etc/grifconfig.conf after first-time installation will take effect only
after the file is reloaded and the media card(s) reset.
Use the grreset command to reset each configured SP Switch Router Adapter card by
specifying the slot number where each card is installed.
Enter:
# grreset < card_slot_number>
Refer to the GRF Reference Guide for more information about using grreset.