GATEWAYS(5) UNIX System V(ANNEX) GATEWAYS(5)
NAME
gateways - Annex network initialization
DESCRIPTION
When an Annex boots, it reads the gateways file from
/usr/spool/erpcd/bfs. This file contains commands to initialize the
routing tables of all Annexes on the local network. In addition, the
gateways file is used in place of EEPROM parameters to initialize SLIP
interfaces on Annex I's.
For routing information, the Annex gateways file has a format that
corresponds closely to the /etc/gateways file used by routed(8C). That
is, you can prep the Annex routing table with routes for networks and
hosts. However, a few differences exist. The basic entry has the
format:
{net|host} addr1 gateway addr2 metric value {passive|hardwired}
Since the RIP implementation on an Annex is listen-only and does not
exchange any routing information with other routers, the Annex does not
have the notion of active gateways. Thus, active routes are not
supported in the Annex gateways file. However, a route learned from an
active gateway producing RIP broadcasts will be aged. Thus, if that
gateway stops including a route in its routing updates, the route will
eventually be discarded.
The Annex does support passive gateways, and the keyword passive marks a
route as such. This indicates that the gateway does not generate its own
routing information. The principal effect of a passive route is to keep
a routing entry from being aged and ultimately discarded. However, such
a route can be overridden by a routing update containing a better route
to the destination. The Annex also supports the notion of hardwired (or
fixed) routes, marked by the keyword hardwired. Such a route will never
be changed or deleted, even if a routing update containing a better route
is received by the Annex.
The keywords net and host indicate whether the Internet address addr1
specifies a destination network or host. The Internet address addr2
specifies the gateway via which the destination is reached. Finally, the
metric value indicates the number of hops needed to reach the
destination.
There are a few additional differences between the Annex gateways file
and the /etc/gateways file used by routed(8C). First, all Internet
addresses in the Annex gateways file are required to be specified in
standard Internet dot notation. This is because when the Annex is
reading the gateways file, it is still in the process of booting, and
thus cannot yet do name-to-address translations. Comments can be placed
in the gateways file and are introduced by a ``#'' character anywhere on
a line and terminated by the end of that line. Excess white space in the
file is ignored. Finally, if an Annex has syslogging enabled, it will
report errors encountered while reading the gateways file with an
extensive selection of syslog messages. The messages are self-
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descriptive and include the line number of the offending line. Various
information useful for only for debugging is logged at the the info and
debug levels.
In addition to routing information, there are currently two other types
entries possible in the gateways file. First, there is the conditional:
annex addr
...
else
...
end
The ellipses represent any group of entries normally valid in the
gateways file. This conditional causes all the entries in the first set
of ellipses to be evaluated only on the Annex that uses the given
Internet address addr for its Ethernet interface. The optional else
clause causes all the entries in the second set of ellipses to be
evaluated on all Annexes, except for the Annex that matched the annex
clause. This can be used to selectively assign routes to hosts, such as
only giving a default route to an external gateway to certain Annexes.
Its usual use is to limit the scope of an ifconfig entry to the
individual Annex with the actual SLIP interface.
The second additional entry is used for defining SLIP interfaces on Annex
I's. This is used because original Annexes do not have the EEPROM space
for storing the parameters associated with a SLIP interface. The format
of the entry is:
ifconfig slN localaddr remoteaddr [ netmask mask ] [ metric number
]
This entry is similar in function to the ifconfig(8C). command. The
individual interface is identified by N, which is the Annex serial port
number. Localaddr and remaddr are the local and remote endpoint
addresses for the point-to-point link, respectively. The optional
netmask keyword sets the subnet mask mask to be used on this interface.
If missing, the subnet mask is defaulted based upon the Internet address
class of localaddr. The optional metric keyword sets the interface
metric number for this interface. These parameters correspond to the na
parameters sliplocaladdress, slipremoteaddress, slipsubnetmask, and
slipmetric used on Annex II's. An Annex II will ignore any ifconfig
entries in the gateways file.
The following is an example of configuring a SL/IP interface on port 6 of
an original Annex.
# SL/IP link to the 192.5.63 net
annex 63.34
# configure the interface itself
ifconfig sl6 61.1 61.2
# recognize the "local" side as yourself
host 61.0.01 gateway 127.1 metric 0 hardwired
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GATEWAYS(5) UNIX System V(ANNEX) GATEWAYS(5)
# 61.2 is a gateway to the entire 192.5.63.0 network
net 192.5.63.0 gateway 61.2 metric 1 hardwired
else
# other Annexes will route to 192.5.63.0 via 63.34
net 192.5.63.0 gateway 63.34 metric 1 hardwired
end
BUGS
The current implementation does not allow the annex/else/end clause to be
nested. That is, you cannot use another annex conditional while already
in the scope of another annex or else clause. While an error message
will not be generated if they are nested, the results will not be what is
expected.
FILES
/usr/spool/erpcd/bfs/gateways
SEE ALSO
erpcd(8), routed(8C)
Annex Network Administrator's Guide
Annex R4.0 Release Notes
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