OSPF user documentation added.
This commit is contained in:
parent
2e9b24211a
commit
8fd12e6b27
1 changed files with 187 additions and 0 deletions
187
doc/bird.sgml
187
doc/bird.sgml
|
@ -877,6 +877,193 @@ protocol kernel { # Secondary routing table
|
||||||
|
|
||||||
<sect>OSPF
|
<sect>OSPF
|
||||||
|
|
||||||
|
<sect1>Introduction
|
||||||
|
|
||||||
|
<p>Open Shortest Path First (OSPF) is quite complex interior gateway
|
||||||
|
protocol. Today's version for IPv4 is 2 and it's defined in RFC 2328<htmlurl
|
||||||
|
url="ftp://ftp.rfc-editor.org/in-notes/rfc2328.txt">. It's based on
|
||||||
|
link-state of SPF technology. Each router maintains a database
|
||||||
|
describing the Autonomous System's topology. Each participating router has
|
||||||
|
has an identical database and all routers run the exact same algorithm
|
||||||
|
calculatin shortest path tree with themselves as roots, in parallel.
|
||||||
|
OSPF chooses the least cost path as the best path. In OSPF, the
|
||||||
|
Autonomous System can be splitted into more areas. Topology
|
||||||
|
of such area is hidden to the rest of the Autonomous System. This enables
|
||||||
|
a reduction in routing traffic as well as protection other areas from bad
|
||||||
|
routing data. Unfortunatelly multiple OSPF areas are not fully supported
|
||||||
|
in this version of BIRD. Another very important feature of OSPF is that
|
||||||
|
it can keep routing information from other protocols (like static or BGP)
|
||||||
|
in it's link-state database as external routes. Each external route can
|
||||||
|
be tagged by the advertising router, enabling the passing of additional
|
||||||
|
information between routers on the boundary of the Autonomous System.
|
||||||
|
|
||||||
|
<p>OSPF quickly detects topological changes in the Autonomous System (such
|
||||||
|
as router interface failures) and calculates new loop-free routes after a
|
||||||
|
period of convergence. This period of convergence is short and involves
|
||||||
|
a minimum of routing traffic.
|
||||||
|
|
||||||
|
<p>Each router joined in OSPF periodically sends hello messages out
|
||||||
|
all its interfaces. This allows neighbors to be discovered dynamically.
|
||||||
|
Then the neighbors exchange theirs parts of database. And keep it
|
||||||
|
identical flooding updates. Flooding proces is reliable and ensures
|
||||||
|
that each routes detects the change.
|
||||||
|
|
||||||
|
<sect1>Configuration
|
||||||
|
|
||||||
|
<p>
|
||||||
|
|
||||||
|
<code>
|
||||||
|
protocol ospf <name> {
|
||||||
|
rfc1583compat bool;
|
||||||
|
area <id> {
|
||||||
|
stub <bool>;
|
||||||
|
tick <num>;
|
||||||
|
interface <interface>
|
||||||
|
{
|
||||||
|
cost <num>;
|
||||||
|
hello <num>;
|
||||||
|
retransmit <num>;
|
||||||
|
priority <num>;
|
||||||
|
wait <num>;
|
||||||
|
dead count <num>;
|
||||||
|
type [broadcast|nonbroadcast|pointopoint];
|
||||||
|
authetication [none|simple];
|
||||||
|
password "<text>";
|
||||||
|
neighbors {
|
||||||
|
<ip>;
|
||||||
|
};
|
||||||
|
};
|
||||||
|
};
|
||||||
|
}
|
||||||
|
</code>
|
||||||
|
|
||||||
|
<descrip>
|
||||||
|
<tag>rfc1583compat <M>bool</M></tag>
|
||||||
|
This option can disable or enable compatibility of routing table
|
||||||
|
calculation with RFC 1583<htmlurl
|
||||||
|
url="ftp://ftp.rfc-editor.org/in-notes/rfc1583.txt">. Default
|
||||||
|
value is no.
|
||||||
|
|
||||||
|
<tag>area <M>id</M></tag>
|
||||||
|
This specifies area id of configured OSPF area. It can be written
|
||||||
|
as a number or as an IPv4 number. The most important area is
|
||||||
|
the backbone (area id 0) to which every other area must be connected.
|
||||||
|
|
||||||
|
<tag>stub <M>bool</M></tag>
|
||||||
|
No external routes are flooded into stub area. Default value is no.
|
||||||
|
|
||||||
|
<tag>tick <M>num</M></tag>
|
||||||
|
The routing table calculation is not processed when any single
|
||||||
|
change comes. To lower the CPU utilization it's processed late
|
||||||
|
in periodical interval. The default value is 7.
|
||||||
|
|
||||||
|
<tag>interface <M>interface</M></tag>
|
||||||
|
This mean that specified interface (or interface pattern) belongs
|
||||||
|
to actual area.
|
||||||
|
|
||||||
|
<tag>cost <M>num</M></tag>
|
||||||
|
Specifies output cost of interface. Default value is 10.
|
||||||
|
|
||||||
|
<tag>hello <M>num</M></tag>
|
||||||
|
Specifies interval between sending hello messages. Beware, all
|
||||||
|
router on the same network has to have the same hello interval.
|
||||||
|
Default value is 10.
|
||||||
|
|
||||||
|
<tag>retransmit <M>num</M></tag>
|
||||||
|
Specifies interval between retransmiting unacknoledged update.
|
||||||
|
Default value is 5.
|
||||||
|
|
||||||
|
<tag>priority <M>num</M></tag>
|
||||||
|
On every multiple access network (like e.g ethernet) Designed
|
||||||
|
and Backup Designed router is elected. These routers have some
|
||||||
|
special functions in flooding process. Higher priority rices
|
||||||
|
preferences in elections. Routers with priority 0 are not
|
||||||
|
eligible. Default value is 1.
|
||||||
|
|
||||||
|
<tag>wait <M>num</M></tag>
|
||||||
|
After start, router waits specified interval between starting
|
||||||
|
election and building adjacency. Default value is 40.
|
||||||
|
|
||||||
|
<tag>dead count <M>num</M></tag>
|
||||||
|
When router does not receive any message from neighbor in
|
||||||
|
<dead count>*<hello> seconds, it will declare neighbor down.
|
||||||
|
|
||||||
|
<tag>type <M>broadcast</M><tag>
|
||||||
|
BIRD detects a type of connected network. However, sometimes is
|
||||||
|
necessary to change it. On broadcast networks are flooding
|
||||||
|
and hello messages sent using multicasting. (Single
|
||||||
|
packet to all neighbors.)
|
||||||
|
|
||||||
|
<tag>type <M>nonbroadcast</M></tag>
|
||||||
|
On nonbroadcast network are packets sent to each neighbor
|
||||||
|
separately because of lack of multicast messages.
|
||||||
|
|
||||||
|
<tag>type <M>pointopoint</M></tag>
|
||||||
|
Pointopoint network connects just 2 routers together. No election
|
||||||
|
is provided there, this reduces a number of sent messages.
|
||||||
|
|
||||||
|
<tag>authetication <M>none</M></tag>
|
||||||
|
No passwords are sent in OSPF's packets. This is default value.
|
||||||
|
|
||||||
|
<tag>authetication <M>simple</M></tag>
|
||||||
|
In every packet is sent an 8 bytes long password. Received packets
|
||||||
|
without this password are ignored. This autentication mechanism is
|
||||||
|
very weak.
|
||||||
|
|
||||||
|
<tag>password <M>text</M></tag>
|
||||||
|
An 8 bytes long password used for authentication.
|
||||||
|
|
||||||
|
<tag>neighbors</tag>
|
||||||
|
A set of neighbors to which hello messages on nonbroadcast networks
|
||||||
|
are sent.
|
||||||
|
</descrip>
|
||||||
|
|
||||||
|
<sect1>Attributes
|
||||||
|
|
||||||
|
<p>OSPF defines 3 route attributes. Each internal route has a metric. External
|
||||||
|
routes uses metric type 1 or metric type 2. Metric type one is comparable
|
||||||
|
with internal metric. Metric type 2 is always longer then metric type 1
|
||||||
|
or internal metric. Each external route can also carry a tag. Tag is
|
||||||
|
32 bits long number and it's used for exporting routes to other protocols
|
||||||
|
in link-state it has no funtion.
|
||||||
|
|
||||||
|
<sect1>Example
|
||||||
|
|
||||||
|
<p>
|
||||||
|
|
||||||
|
<code>
|
||||||
|
protocol ospf MyOSPF {
|
||||||
|
area 0.0.0.0 {
|
||||||
|
tick 8;
|
||||||
|
interface "eth*" {
|
||||||
|
cost 11;
|
||||||
|
hello 15;
|
||||||
|
priority 100;
|
||||||
|
retransmit 7;
|
||||||
|
authentication simple;
|
||||||
|
password "aaa";
|
||||||
|
};
|
||||||
|
interface "ppp*" {
|
||||||
|
cost 100;
|
||||||
|
};
|
||||||
|
};
|
||||||
|
area 120 {
|
||||||
|
stub yes;
|
||||||
|
interface "-arc0" , "arc*" {
|
||||||
|
type nonbroadcast;
|
||||||
|
authentication none;
|
||||||
|
wait 50;
|
||||||
|
dead count 6;
|
||||||
|
neighbors {
|
||||||
|
192.168.120.1;
|
||||||
|
192.168.120.2;
|
||||||
|
192.168.120.10;
|
||||||
|
};
|
||||||
|
};
|
||||||
|
};
|
||||||
|
}
|
||||||
|
</code>
|
||||||
|
|
||||||
<sect>Pipe
|
<sect>Pipe
|
||||||
|
|
||||||
<sect1>Introduction
|
<sect1>Introduction
|
||||||
|
|
Loading…
Reference in a new issue