HP-UX Reference (11i v1 05/09) - 1M System Administration Commands N-Z (vol 4)

r
route(1M) route(1M)
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. For IPv4, the default IP address and netmask of the loopback interface are 127.0.0.1 and
255.0.0.0, respectively. For IPv6, the default IP address and prefix of the loopback interface are ::1 and
128, respectively.
When lo0 is configured, the 127.0.0.0 loopback route for IPv4 and the ::1 loopback route for IPv6 are set
up automatically so that packets for any 127.*.*.* address and ::1 will loop back to the local host. Users
cannot add or delete any 127.*.*.* or ::1 loopback routes.
IPv6 Operation
The keyword inet6 is required for adding or deleting IPv6 routes.
Examples
add a direct IPv6 host route
route inet6 add 2345::1 4444::3
add an indirect IPv6 (sub)network route
route inet6 add net 2222::/64 4567::8 1
delete an indirect IPv6 (sub)network route
route inet6 delete net 2222::/64 4567::8 1
add a configured tunnel for a remote network
route inet6 -t add net 2233::/66 ::12.13.14.15 1
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−−776 Hewlett-Packard Company − 3 − HP-UX 11i Version 1: September 2005