HP-UX Reference (11i v1 00/12) - 1M System Administration Commands N-Z (vol 4)

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route(1M) route(1M)

• A host name (the ofﬁcial name or an alias, see gethostent(3N)).

• An Internet address in dot notation (see inet(3N)).

count An integer that indicates whether the gateway is a remote host or the local host. If

the route leads to a destination through a remote gateway, count should be a number

greater than 0. If the route leads to destination and the gateway is the local host,

count should be 0. The default for count is zero. The result is not deﬁned if count is

negative.

Operation

All symbolic names speciﬁed for a destination or gateway are looked up ﬁrst as a host name using

gethostbyname(); if the host name is not found, the destination is searched for as a network name

using getnetbyname(). destination and gateway can be in dot notation (see inet(3N)).

If the -n option is not speciﬁed, any host and network addresses are displayed symbolically according to

the name returned by gethostbyaddr() and getnetbyaddr(), respectively, except for the default

network address (printed as default) and addresses that have unknown names. Addresses with

unknown names are printed in Internet dot notation (see inet(3N)).

If the -n option is speciﬁed, any host and network addresses are printed in Internet dot notation except for

the default network address which is printed as default

If the

-f option is speciﬁed, route deletes all route table entries that specify a remote host for a gateway.

If it is used with one of the subcommands described above, the entries are deleted before the subcommand

is processed.

Path MTU Discovery is a technique for discovering the maximum size of an IP datagram that can be sent

on an internet path without causing datagram fragmentation in the intermediate routers. In essence, a

source host that utilizes this technique initially sends out datagrams up to the the size of the outgoing

interface. The Don’t Fragment (DF) bit in the IP datagram header is set. As an intermediate router that

supports Path MTU Discovery receives a datagram that is too large to be forwarded in one piece to the

next-hop router and the DF bit is set, the router will discard the datagram and send an ICMP Destination

Unreachable message with a code meaning "fragmentation needed and DF set". The ICMP message will

also contain the MTU of the next-hop router. When the source host receives the ICMP message, it reduces

the path MTU of the route to the MTU in the ICMP message. With this technique, the host route in the

source host for this path will contain the proper MTU.

The -p pmtu option is useful only if you know the network environment well enough to enter an appropri-

ate pmtu for a host or network route. IP will fragment a datagram to the pmtu speciﬁed for the route on

the local host before sending the datagram out to the remote. It will avoid fragmentation by routers along

the path, if the pmtu speciﬁed in the

route command is correct.

ping can be used to ﬁnd the pmtu information for the route to a remote host. The pmtu information in

the routing table can be displayed with the

netstat -r command (see netstat(1)).

The loopback interface (lo0) is automatically conﬁgured when the system boots with the TCP/IP

software. The default IP address and netmask of the loopback interface are 127.0.0.1 and 255.0.0.0, respec-

tively.

The 127.0.0.0 loopback route is set up automatically when lo0 is conﬁgured so that packets for any

127.*.*.* address will loop back to the local host. Users cannot add or delete any 127.*.*.* loopback routes.

Output

add destination: gateway gateway

The speciﬁed route is being added to the tables.

delete destination: gateway gateway

The speciﬁed route is being deleted from the tables.

Flags

The values of the count and destination type ﬁelds in the route command determine the presence of the G

and H ﬂags in the netstat -r display and thus the route type, as shown in the following table.

Section 1M−−730 − 2 − HP-UX Release 11i: December 2000

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