Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 45)

Using a DNS name to initiate a trace route
Suppose you want to trace the route from a BrocadeLayer 3 switch to a remote server identified as
NYC02 on domain newyork.com. Because the [email protected] domain is already defined on
the Layer 3 switch, you need to enter only the host name, NYC02, as noted in the following example.
device# traceroute nyc02
Syntax: traceroute [ vrf vrf ] host-ip-addr [ maxttlvalue ] [ minttl value ] [ numeric ] [ timeout value ] [
source-ip ip add r]
The only required parameter is the IP address of the host at the other end of the route.
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. When
traceroute fails, an error occurs as shown in the last two lines in the given example.
Type Control-c to abort
Sending DNS Query to 10.157.22.199
Tracing Route to IP node 10.157.22.80
To ABORT Trace Route, Please use stop-traceroute command.
Traced route to target IP node 10.157.22.80:
IP Address Round Trip Time1 Round Trip Time2
10.95.6.30 93 msec 121 msec
Trace route to target IP node 10.157.22.80 failed.
IP: Errno(9) No response from target or intermediate node
NOTE
In the previous example, 10.157.22.199 is the IP address of the domain name server (default DNS
gateway address), and 10.157.22.80 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.
‐ Port MTU - A port default MTU depends on the encapsulation type enabled on the port.
Changing the encapsulation type
The Layer 3 switch encapsulates IP packets into Layer 2 packets, to send the IP packets on the
network. (A Layer 2 packet is also called a MAC layer packet or an Ethernet frame.) The source
address of a Layer 2 packet is the MAC address of the Layer 3 switch interface sending the packet. The
destination address can be one of the following:
• The MAC address of the IP packet destination. In this case, the destination device is directly
connected to the Layer 3 switch.
• The MAC address of the next-hop gateway toward the packet destination.
• An Ethernet broadcast address.
Using a DNS name to initiate a trace route
FastIron Ethernet Switch Layer 3 Routing Configuration Guide 45
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