HP-UX Reference (11i v1 05/09) - 4 File Formats (vol 8)

g
gated.conf(4) gated.conf(4)
Groups
BGP peers are grouped by type and the autonomous system of the peers. Any number of groups may be
specified, but each must have a unique combination of type and peer autonomous system. There are four
possible group types:
group type external peeras autonomous_system
In the classic external BGP group, full policy checking is applied to all incoming and outgoing
advertisements. The external neighbors must be directly reachable through one of the local inter-
faces of the machine . By default no metric is included in external advertisements, and the next
hop is computed with respect to the shared interface.
group type internal peeras autonomous_system
An internal group operating where there is no IP-level IGP, for example an SMDS network or
MILNET. All neighbors in this group are required to be directly reachable via a single interface.
All next hop information is computed with respect to this interface. Import and export policy
may be applied to group advertisements. Routes received from external BGP or EGP neighbors
are by default readvertised with the received metric.
group type igp peeras autonomous_system proto proto
An internal group that runs in association with an interior protocol. The IGP group examines
routes which the IGP is exporting and sends an advertisement only if the path attributes could
not be entirely represented in the IGP tag mechanism. Only the AS path, path origin, and transi-
tive optional attributes are sent with routes. No metric is sent, and the next hop is set to the
local address used by the connection. Received internal BGP routes are not used or readvertised.
Instead, the AS path information is attached to the corresponding IGP route and the latter is
used for readvertisement. Since internal IGP peers are sent only a subset of the routes which the
IGP is exporting, the export policy of the IGP is used. There is no need to implement the "don’t
routes from peers in the same group" constraint since the advertised routes are routes that IGP
already exports.
group type routing peeras autonomous_system proto proto interface interface_list
An internal group which uses the routes of an interior protocol to resolve forwarding addresses.
A type routing group propagates external routes between routers which are not directly con-
nected. A type routing group computes immediate next hops for these routes by using the BGP
next hop which arrived with the route as a forwarding address. The forwarding address is to be
resolved via the routing information of an internal protocol. In essence, internal BGP is used to
carry AS external routes, while the IGP is expected to only carry AS internal routes, and the
latter is used to find immediate next hops for the former.
The proto names the interior protocol to be used to resolve BGP route next hops, and may be the
name of any IGP in the configuration. By default the next hop in BGP routes advertised to type
routing peers will be set to the local address on the BGP connection to those peers, as it is
assumed a route to this address will be propagated via the IGP. The interface_list can optionally
provide a list interfaces whose routes are carried via the IGP for which third party next hops
may be used instead.
group type test peeras autonomous_system
An extension to external BGP which implements a fixed policy using test peers. Fixed policy and
special case code make test peers relatively inexpensive to maintain. Test peers do not need to be
on a directly attached network. If GateD and the peer are on the same (directly attached) sub-
net, the advertised next hop is computed with respect to that network. Otherwise the next hop is
the current next hop of the local machine. All routing information advertised by and received
from a test peer is discarded, and all BGP routes that can be advertised are sent back to the test
peer. Metrics from EGP-derived and BGP-derived routes are forwarded in the advertisement.
Otherwise no metric is included.
Group parameters
The BGP statement has group clauses and peer subclauses. Any number of peer subclauses may be
specified within a group. A group clause usually defines default parameters for a group of peers, these
parameters apply to all subsidiary peer subclauses. Any parameters from the peer subclause may be
specified on the group clause to provide defaults for the whole group (which may be overridden for indivi-
dual peers).
HP-UX 11i Version 1: September 2005 − 28 − Hewlett-Packard Company Section 4−−97