Configuring Packet Parameters - Foundry Networks FESX Manual

Foundry Configuration Guide for the FESX, FSX, and FWSX
Defining a DNS Entry
You can define up to four DNS servers for each DNS entry. The first entry serves as the primary default address.
If a query to the primary address fails to be resolved after three attempts, the next gateway address is queried
(also up to three times). This process continues for each defined gateway address until the query is resolved.
The order in which the default gateway addresses are polled is the same as the order in which you enter them.
Suppose you want to define the domain name of newyork.com on a Layer 3 Switch and then define four possible
default DNS gateway addresses. To do so, enter the following commands:
FESX424 Router(config)# ip dns domain-name newyork.com
FESX424 Router(config)# ip dns server-address 209.157.22.199 205.96.7.15 208.95.7.25
201.98.7.15
Syntax: ip dns server-address <ip-addr> [<ip-addr>] [<ip-addr>] [<ip-addr>]
In this example, the first IP address in the ip dns server-address... command becomes the primary gateway
address and all others are secondary addresses. Because IP address 201.98.7.15 is the last address listed, it is
also the last address consulted to resolve a query.
Using a DNS Name To Initiate a Trace Route
Suppose you want to trace the route from a Foundry Layer 3 Switch to a remote server identified as NYC02 on
domain newyork.com. Because the newyork.com domain is already defined on the Layer 3 Switch, you need to
enter only the host name, NYC02, as noted below.
FESX424 Router# traceroute nyc02
Syntax: traceroute <host-ip-addr> [maxttl <value>] [minttl <value>] [numeric] [timeout <value>]
[source-ip <ip addr>]
The only required parameter is the IP address of the host at the other end of the route. See the Foundry Switch
and Router Command Line Interface Reference for information about the parameters.
After you enter the command, a message indicating that the DNS query is in process and the current gateway
address (IP address of the domain name server) being queried appear on the screen:
Type Control-c to abort
Sending DNS Query to 209.157.22.199
Tracing Route to IP node 209.157.22.80
To ABORT Trace Route, Please use stop-traceroute command.
Traced route to target IP node 209.157.22.80:
IP Address
207.95.6.30
NOTE: In the above example, 209.157.22.199 is the IP address of the domain name server (default DNS
gateway address), and 209.157.22.80 represents the IP address of the NYC02 host.

Configuring Packet Parameters

You can configure the following packet parameters on Layer 3 Switches. These parameters control how the Layer
3 Switch sends IP packets to other devices on an Ethernet network. The Layer 3 Switch always places IP packets
into Ethernet packets to forward them on an Ethernet port.
• Encapsulation type – The format for the Layer 2 packets within which the Layer 3 Switch sends IP packets.
• Maximum Transmission Unit (MTU) – The maximum length of IP packet that a Layer 2 packet can contain. IP
packets that are longer than the MTU are fragmented and sent in multiple Layer 2 packets. You can change
the MTU globally or an individual ports.
• Global MTU – The default MTU value depends on the encapsulation type on a port and is 1500 bytes for
Ethernet II encapsulation and 1492 bytes for SNAP encapsulation.
16 - 20
Round Trip Time1
93 msec
© Foundry Networks, Inc.
Round Trip Time2
121 msec
December 2005