HP-UX Reference (11i v1 00/12) - 4 File Formats (vol 8)
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STANDARD Printed by: Nora Chuang [nchuang] STANDARD
/build/1111/BRICK/man4/!!!intro.4
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g
gated.conf(4) gated.conf(4)
open
BGP OPEN packets which are used to establisha peer relationship.
update
BGP UPDATE packets which are used to pass network reachability information.
keepalive
BGP KEEPALIVE packets which are used to verify peer reachability.
The ICMP Statement
On systems without the BSD routing socket, gated listens to ICMP messages received by the system.
Currently gated only does processing on ICMP redirect packets, but more functionality may be added in the
future, such as support for the router discovery messages. Processing of ICMP redirect messages is handled
by the redirect statement.
Currently the only reason to specify the icmp statement is to be able to trace the ICMP messages that
gated receives.
The ICMP statement
icmp {
traceoptions trace_options ;
}
traceoptions trace_options ;
Specifies the tracing options for ICMP. (See Trace Statements and the ICMP specific tracing options
below.)
Tracing options
Packet tracing options (which may be modified with detail and recv):
packets
All ICMP packets received.
redirect
Only ICMP REDIRECT packets received.
routerdiscovery
Only ICMP ROUTER DISCOVERY packets received.
info Only ICMP informational packets, which include mask request/response, info request/response,
echo request/response and time stamp request/response.
error
Only ICMP error packets, which include time exceeded, parameter problem, unreachable and
source quench.
Redirect Processing
The redirect code is passed ICMP or ISO redirects learned by monitoring ICMP messages, or via the
routing socket on systems that support it. It processes the redirect request and decides whether to accept
the redirect. If the redirect is accepted, a route is installed in the gated routing table with the protocol
redirect. Redirects are deleted from the routing table after 3 minutes.
If GateD determines that a redirect is not acceptable, it tries to figure out if the kernel forwarding table has
been modified. On systems where ICMP messages are monitored this is accomplished by trying to second
guess what the kernel would have done with the redirect. On systems with the routing socket, the kernel
provides and indication of whether the redirect was accepted; GateD ignores redirects that were not pro-
cessed.
If GateD has determined that the state of the kernel forwarding table has been changed, the necessary
requests to the kernel are made to restore the correct state.
Note that on currently available systems it is not possible to disable the processing of ICMP redirects, even
when the system is functioning as a router. To ignore the effects of redirects, GateD must process each one
and actively restore any changes it made to the state of the kernel. Because of the mechanisms involved,
there will be windows where the effects of redirects are present in the kernel.
By default, GateD removes redirects when actively participating in an interior gateway protocol (RIP,
HELLO, OSPF or IS-IS). It is not possible to enable redirects once they have been automatically disabled.
Listening to RIP or HELLO in nobroadcast mode does not cause redirects to be ignored, nor does the use of
Section 4−−102 − 31 − HP-UX Release 11i: December 2000
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