Vyatta NOS documentation

Learn how to install, configure, and operate Vyatta Network Operating System (Vyatta NOS), which helps to drive our virtual networking and physical platforms portfolio.

ping <host> mtu-discovery < do | dont | want > <option>

Selects the discovery strategy of the path maximum transmission unit (PMTU).

ping{ ipv4_address | ipv6_address | hostname } mtu-discovery { do | dont | want } option
ipv4_address
The IPv4 address of the host.
ipv6_address
The IPv6 address of the host.
hostname
A host being pinged. This keyword is used when the host is specified as a host name rather than as an IP address.
do

Prohibits fragmentation, even for the local packet. Sets a do-not fragment (DF) flag to the router.

want

Performs a PMTU discovery. During the discovery the device fragments the packet locally.

dont
Prohibits fragmentation, but does not set a DF flag.
option
Each of the following entries are considered options. These options can be issued consecutively, that is, in the same command line.
adaptive
Adaptively sets interpacket interval.
allow-broadcast
Allows you to ping broadcast address.
audible
Makes a beep sound on every ping, while the device pings for host details.
bypass-route
Bypasses normal routing tables during ping.
count
Specifies the number of ping requests to send.
deadline
Specifies the number of seconds before which ping expires.
ether-size
Matches the overall size of the data packet with the resultant size of the Layer 3 packet.
flood
Sends 100 ping requests each second.
interface
Specifies an interface that the device must use as the source address.
interval
Specifies the time in seconds for which the device must wait between ping requests.
mark
Specifies that the device must consider the ping request for special processing.
mtu-discovery
Specifies the path MTU discovery strategy.
no-loopback
Suppresses loop-back of multicast pings.
numeric
Does not resolve domain name system (DNS) names during ping.
pattern
Specifies the hexadecimal digit pattern to fill the packet.
quiet
Prints only the ping summary page.
record-route
Records the route that the packet takes.
size
Specifies the number of bytes to send for a ping request.
timestamp
Displays the timestamp during ping output.
tos
Marks packet with specified type of service (TOS).
ttl
Specifies the maximum packet life-time for a host.
verbose
Displays a detailed output for the ping command.

Operational mode

The ping host mtu-discovery command selects the discovery strategy of the PMTU, based on the parameters provided. The command checks the size of the packet. If the size is equal to or greater than the maximum data payload that is available in a packet, the device determines whether the packet has to be fragmented, based on the discovery strategy of the PMTU.

This example shows how to test 1472 bytes of data of the host 10.0.0.103 for network reachability while prohibiting network fragmentation during the ping. However a do-not-fragment flag is set for the router.

vyatta@vyatta:~$ ping 10.0.0.103 size 1472 mtu-discovery do
PING 10.0.0.103 (10.0.0.103) 1472(1500) bytes of data.
1480 bytes from 10.0.0.103: icmp_req=1 ttl=64 time=0.923 ms
^[[A1480 bytes from 10.0.0.103: icmp_req=2 ttl=64 time=1.35 ms
^C
--- 10.0.0.103 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 999ms
rtt min/avg/max/mdev = 0.923/1.137/1.352/0.217 ms

This example shows how to test 1472 bytes of data of the host 10.0.0.103 for network reachability while prohibiting network fragmentation during the ping. However a do-not-fragment flag is not set for the router.

vyatta@VR-1:~$ ping 10.0.0.103 size 1472 mtu-discovery dont
PING 10.0.0.103 (10.0.0.103) 1472(1500) bytes of data.
1480 bytes from 10.0.0.103: icmp_req=1 ttl=64 time=1.25 ms
^C
--- 10.0.0.103 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.250/1.250/1.250/0.000 ms

This example shows how to perform a discovery strategy for PMTU during a ping request. During the discovery, the router fragments the packet locally.

vyatta@VR-1:~$ ping 10.0.0.103 size 1472 mtu-discovery want
PING 10.0.0.103 (10.0.0.103) 1472(1500) bytes of data.
1480 bytes from 10.0.0.103: icmp_req=1 ttl=64 time=1.00 ms
^C
--- 10.0.0.103 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.005/1.005/1.005/0.000 ms