3Com Router User Manual

							Configuring OSPF437
Ta b l e 503   Configure Route Import for OSPF
By default, OSPF does not import routes from other domains into the routing 
table.
The protocol attribute specifies the source routing domain that can be imported. 
At present, OSPF can import routes domain such as connected, static, RIP, and 
BGP.
See“Configuring Route Import for OSPF” for the details of routing import.
Configuring Parameters 
when Importing 
External RoutesWhen the routes found by other routing protocols on the router are received by 
OSPF as the external routing information of its own AS, some other parameters 
are needed, including the default cost and default tag of the route. Router tag can 
be used to identify the information related to the protocol, such as the number 
OSPF uses as the AS number when receiving BGP protocol.
OSPF specifies two types of cost selection modes of external routing information in 
the protocol. You can configure receiving the default cost type of the route.
Perform the following configurations in OSPF view.
Ta b l e 504   Configure Parameters When Importing External Routes
OperationCommand
Configure route import for OSPFimport-route protocol [ cost cost ] [ 
type 1 | 2 ] [ tag tag-value ] [ 
route-policy policy-name ]
Cancel route distribution for OSPFundo import-route protocol [ cost 
cost ] [ type 1 | 2 ] [ tag tag-value 
] [ route-policy policy-name ]
OperationCommand
Configure the default cost value when 
OSPF importing external routesdefault import-route cost cost
Return to the default cost value when 
OSPF importing external routesundo default import-route cost
Configure the interval for OSPF importing 
external routesdefault import-route interval 
seconds
Return to the default interval value for 
OSPF importing external routesundo default import-route interval 
seconds
Configure the upper limit of routes that 
OSPF can importdefault import-route limit routes
Restore default value of routes that OSPF 
can importundo default import-route limit
Configure the default tag value when 
OSPF importing external routesdefault import-route tag tag
Return to the default tag value when OSPF 
importing external routesundo default import-route tag
Configure the default type when OSPF 
importing external routesdefault import-route type { 1 | 2 }
Return to the default route type when 
OSPF importing external routesundo default import-route type 
						

							438CHAPTER 29: CONFIGURING OSPF
By default, the cost value is 1, and the tag value is 1. The imported route is 
external route Type 2, the interval of importing external route is 1 second and at 
most 150 external routes can be imported in each interval.
Setting Route PreferenceMultiple dynamic routing protocols may be executed on the router at the same 
time, the problem of information sharing and selection between the routing 
protocols can occur. The system sets a priority for every routing protocol. When 
several protocols find the same route, the protocol with higher priority will 
supercede.
Perform the following configurations in OSPF view.
Ta b l e 505   Set Route Preference
By default, OSPF route preference is 10. The preference of the imported external 
routing protocol is 150.
Configuring a Route 
Filter for OSPFPerform the following configurations in OSPF view.
Configure filtering route information received by OSPF.
Ta b l e 506   Filter the Routing Information Received by OSPF
By default, OSPF does not filter any route information received.
Displaying and 
Debugging OSPFTa b l e 507   Display and Debug OSPF
OperationCommand
Specify OSPF route preferencepreference [ ase ] value
Return the default value of OSPF route 
preferenceundo preference [ ase ]
OperationCommand
Filter the routing information receivedfilter-policy acl-number import
Change or cancel filtering routing 
information receivedundo filter-policy acl-number import
OperationCommand
Display OSPF main informationdisplay ospf 
Display OSPF external routing informationdisplay ospf ase [ retranse ]
Display OSPF statistic informationdisplay ospf cumulative
Display OSPF LSDB informationdisplay ospf database [ retranse ]
Display OSPF error informationdisplay ospf error
Display OSPF interface informationdisplay ospf interface 
interface-type interface-number
Display OSPF LSDB detailed informationdisplay ospf lsa [ router_lsa | 
net_lsa | sumnet_lsa | asbr_lsa | 
external_lsa | nssa_external_lsa | 
adv_rtr | self_originate | ls_id ] [ 
area area-id ]
Display OSPF neighboring point 
informationdisplay ospf peer  
Display OSPF nexthop informationdisplay ospf nexthop 
						

							OSPF Configuration Example439
OSPF Configuration 
ExampleThis section describes several different configurations of OSPF with a suggested 
procedure for each configuration
Configuring OSPF on the 
Point-to-Multipoint 
Network.The configuration for this example includes the following features:
■Router A communicates with Router B through DLCI 101, communicates with 
Router C through DLCI 102, and communicates with Router E through DLCI 
103.
■Router B communicates with Router A through DLCI 201 and communicates 
with Router C through DLCI 202.
■Router C communicates with Router A through DLCI 301 and communicates 
with Router B through DLCI 302.
■Router D communicates with Router E through DLCI 401.
■Router E communicates with Router A through DLCI 501 and communicates 
with Router D through DLCI 502.
Figure 147   Networking diagram of running OSPF on point-to-multipoint interface
To configure OSPF on the point-to-multipoint network
1Configure Router A:
aConfigure the ip address of interface Serial0, encapsulated into frame relay and 
configure frame relay mapping table.
Display OSPF routing table informationdisplay ospf routing
Display the information about OSPF virtual 
linksdisplay ospf vlink
Turn on the OSPF debugging packet 
switchesdebugging ospf { event | packet [ ack 
| dd | hello | request | update ] | 
lsa | spf }
Turn off the OSPF debugging packet 
switchesundo debugging ospf { event | packet 
[ ack | dd | hello | request | update 
] | lsa | spf }
Operation Command
FR 1.1.1.1
1.1.1.2
1.1.1.3
1.1.1.4 Router ARouter B
Router DRouter C
s0s0
s0 s0
101
102
103201
202
Router E
501
502
s0401
301
302
1.1.1.5 
						

							440CHAPTER 29: CONFIGURING OSPF
[RouterA] interface serial 0
[RouterA-Serial0] ip address 1.1.1.1 255.0.0.0
[RouterA-Serial0] link-protocol fr
[RouterA-Serial0] fr map IP 1.1.1.2 dlci 101 broadcast
[RouterA-Serial0] fr map IP 1.1.1.3 dlci 102 broadcast
[RouterA-Serial0] fr map IP 1.1.1.4 dlci 103 broadcast
bEnable OSPF
[RouterA-Serial0] quit
[RouterA] router id 1.1.1.1
[RouterA] ospf enable
[RouterA-ospf] quit
cConfigure the area-id of the interface and the interface type
[RouterA] interface serial 0
[RouterA-Serial0] ospf enable area 0
[RouterA-Serial0] ospf network-type p2mp
[RouterA-Serial0] ospf peer 1.1.1.2
[RouterA-Serial0] ospf peer 1.1.1.3
[RouterA-Serial0] ospf peer 1.1.1.4
2Configure Router B:
aConfigure the ip address of interface Serial0, encapsulated into frame relay and 
configure frame relay mapping table.
[RouterB] interface serial 0
[RouterB-Serial0] ip address 1.1.1.2 255.0.0.0
[RouterB-Serial0] link-protocol fr
[RouterB-Serial0] fr map ip 1.1.1.1 dlci 201 broadcast
[RouterB-Serial0] fr map ip 1.1.1.3 dlci 202 broadcast
bEnable OSPF
[RouterB-Serial0] quit
[RouterB] router id 2.2.2.2
[RouterB] ospf enable
[RouterB-ospf] quit
cConfigure the area-id of the interface and the interface type
[RouterB] interface serial 0
[RouterB-Serial0] ospf enable area 0
[RouterB-Serial0] ospf network-type p2mp
[RouterB-Serial0] ospf peer 1.1.1.1
[RouterB-Serial0] ospf peer 1.1.1.3
3Configure Router C:
aConfigure the ip address of interface Serial0, encapsulated into frame relay and 
configure frame relay mapping table.
[RouterC] interface serial 0
[RouterC-Serial0] ip address 1.1.1.3 255.0.0.0
[RouterC-Serial0] link-protocol fr
[RouterC-Serial0] fr map IP 1.1.1.1 dlci 301 broadcast
[RouterC-Serial0] fr map IP 1.1.1.2 dlci 302 broadcast
bEnable OSPF
[RouterC-Serial0] quit
[RouterC] router id 3.3.3.3
[RouterC] ospf enable 
						

							OSPF Configuration Example441
cConfigure the area-id of the interface and the interface type
[RouterC-ospf] quit
[RouterC] interface serial 0
[RouterC-Serial0] ospf enable area 0
[RouterC-Serial0] ospf network-type p2mp
[RouterC-Serial0] ospf peer 1.1.1.1
[RouterC-Serial0] ospf peer 1.1.1.2
4Configure Router D:
aConfigure the ip address of interface Serial0, encapsulated into frame relay and 
configure frame relay mapping table.
[RouterD] interface serial 0
[RouterD-Serial0] ip address 1.1.1.4 255.0.0.0
[RouterD-Serial0] link-protocol fr
[RouterD-Serial0] fr map IP 1.1.1.5 dlci 401 broadcast
bEnable OSPF
[RouterD] router id 4.4.4.4
[RouterD] ospf enable
[RouterD-ospf] quit
cConfigure the area-id of the interface and the interface type
[RouterD-Serial0] ospf enable area 0
[RouterD-Serial0] ospf network-type p2mp
[RouterD-Serial0] ospf peer 1.1.1.5
5Configure Router E:
aConfigure the ip address of interface Serial0, encapsulated into frame relay and 
configure frame relay mapping table.
[RouterE] interface serial 0
[RouterE-Serial0] ip address 1.1.1.5 255.0.0.0
[RouterE-Serial0] link-protocol fr
[RouterE-Serial0] fr map IP 1.1.1.1 dlci 501 broadcast
[RouterE-Serial0] fr map IP 1.1.1.4 dlci 502 broadcast
bEnable OSPF
[RouterE-Serial0] quit
[RouterE] router id 5.5.5.5
[RouterE] ospf enable
cConfigure the area-id of the interface and the interface type
[RouterE-ospf] quit
[RouterE] interface serial 0
[RouterE-Serial0] ospf enable area 0
[RouterE-Serial0] ospf network-type p2mp
[RouterE-Serial0] ospf peer 1.1.1.1
[RouterE-Serial0] ospf peer 1.1.1.4
Configure DR on OSPF 
PreferenceI. Networking requirement
The following example describes the configuration of route preference of several 
routers in an OSPF autonomous system. The preference of Router A is 100, the 
highest on the network, therefore Router A is selected as DR. Router C is of the 
second highest priority, therefore is chosen as BDR. The preference of Router B is 
0, which means that it cannot be a DR. Router D has no preference, so the default 
value 1 is taken. 
						

							442CHAPTER 29: CONFIGURING OSPF
II. Networking diagram
Figure 148   Networking diagram of configuring “DR” selection of OSPF preference
III. Configuration procedure
1Configure Router A:
[RouterA] interface ethernet 0
[RouterA-Ethernet0] ip address 192.1.1.1 255.255.255.0
[RouterA-Ethernet0] ospf dr-priority 100
[RouterA-Ethernet0] quit
[RouterA] router id 1.1.1.1
[RouterA] ospf enable 
[RouterA-ospf] interface ethernet 0
[RouterA-Ethernet0] ospf enable area 0
2Configure Router B:
[RouterB] interface ethernet 0
[RouterB-Ethernet0] ip address 192.1.1.2 255.255.255.0
[RouterB-Ethernet0] ospf dr-priority 0
[RouterB-Ethernet0] quit
[RouterB] router id 2.2.2.2
[RouterB] ospf enable
[RouterB-ospf] interface ethernet 0
[RouterB-Ethernet0] ospf enable area 0
3Configure Router C:
[RouterC] interface ethernet 0
[RouterC-Ethernet0] ip address 192.1.1.3 255.255.255.0
[RouterC-Ethernet0] ospf dr-priority 2
[RouterC-Ethernet0] quit
[RouterC] router id 3.3.3.3
[RouterC] ospf enable
[RouterC-ospf] interface ethernet 0
[RouterC-Ethernet0] ospf enable area 0
4Configure Router D:
[RouterD] interface ethernet 0
[RouterD-Ethernet0] ip address 192.1.1.4 255.255.255.0
[RouterD-Ethernet0] quit
[RouterD] router id 4.4.4.4
[RouterD] ospf enable
[RouterD-ospf] interface ethernet 0
[RouterD-Ethernet0] ospf enable area 0
BDR
Router B Router A Router D
Router C
E 0 192.1.1.1/24
E 0 192.1.1.4/24
E 0 10.1.2.3/24
E 0 192.1.1.2/24 DR1.1.1.14.4.4.4
3.3.3.3 2.2.2.2 
						

							OSPF Configuration Example443
Run display ospf peer on Router A to show OSPF peer. Note that Router A has 
3 peers.
[RouterA] display ospf peer
The status of every peer is full, which means that Router A has created 
neighboring relation with all peers. Only DR and BDR have created neighboring 
relation with all routers on the network. Router A is DR and Router C is BDR on the 
network. All other peers are DRother, which means that they are neither DR nor 
BDR.
Change the preference of Router B to 200:
[RouterB-Ethernet0] ospf dr-priority 200
Run display ospf peer on Router A to show OSPF peers. Note that the 
preference of Router B has been changed to 200, but it is not DR.
[RouterA] display ospf peer
Only when the DR no longer exists on the network are the DR changed. Shut 
down Router A and run
 display ospf peer on Router D to display peers. Note 
that Router C, which was BDR, now becomes DR and so does Router B.
[RouterD] display ospf peer
Shutting down the router and restarting leads to the reelection of DR and BDR. 
Restart router A and run the 
display ospf peer command to display peers. Note 
that router B is elected DR (whose preference is 200) and Router A becomes BDR 
(whose preference is 100). 
[RouterD] display ospf peer
PeerpriState AddressInterface
4.4.4.4 1full/DRother 192.1.1.4Ethernet0
3.3.3.32full/BDR 192.1.1.3Ethernet0
2.2.2.20full/DRother 192.1.1.2Ethernet0
PeerpriState AddressInterface
4.4.4.4 1full/DRother 192.1.1.4Ethernet0
3.3.3.32full/BDR 192.1.1.3Ethernet0
2.2.2.2200full/DRother 192.1.1.2Ethernet0
PeerpriState AddressInterface
3.3.3.32full/BDR 192.1.1.3Ethernet0
2.2.2.2200full/DR192.1.1.2Ethernet0
PeerpriState AddressInterface
1.1.1.1100full/BDR 192.1.1.1E0
3.3.3.32full/DRother 192.1.1.3E0
2.2.2.2200full/DR192.1.1.2E0 
						

							444CHAPTER 29: CONFIGURING OSPF
Configuring an OSPF 
Virtual LinkArea 4 is not directly connected with area 0 in the following diagram. Area 1 
serves as the transit area to connect area 4 and area 0. Configure a virtual link 
between Router B and Router C.
Figure 149   Networking diagram of configuring OSPF virtual link
To configure an OSPF virtual link:
1Configure Router A:
[RouterA] interface ethernet 0
[RouterA-Ethernet0] ip address 192.1.1.1 255.255.255.0
[RouterA-Ethernet0] quit
[RouterA] router id 1.1.1.1
[RouterA] ospf enable
[RouterA-ospf] interface ethernet 0
[RouterA-Ethernet0] ospf enable area 0
2Configure Router B:
[RouterB] interface ethernet 0
[RouterB-Ethernet0] ip address 192.1.1.2 255.255.255.0
[RouterB-Ethernet0] interface serial 0
[RouterB-Serial0] ip address 193.1.1.2 255.255.255.0
[RouterB-Serial0] quit
[RouterB] router id 2.2.2.2
[RouterB] ospf enable
[RouterB-ospf] interface ethernet 0
[RouterB-Ethernet0] ospf enable area 0
[RouterB-Ethernet0] interface serial 0
[RouterB-Serial0] ospf enable area 1
[RouterB-Serial0] quit
[RouterB] ospf
[RouterB-ospf] Vlink peer-id 3.3.3.3 transit-area 1 
3Configure Router C:
[RouterC] interface ethernet 0
[RouterC-Ethernet0] ip address 152.1.1.1 255.255.255.0
[RouterC-Ethernet0] interface serial 0
[RouterC-Serial0] ip address 193.1.1.1 255.255.255.0
[RouterC-Serial0] quit
E0 192.1.1.1/24
E0  152.1.1.1/24 E0 192.1.1.2/24
Router B
Vi r tu a l
LinkS0 193.1.1.2/24
Ar e a  2 Ar e a  1Ar e a  0
Router C
3.3.3.3
Router A
2.2.2.21.1.1.1
S0 193.1.1.1/24 
						

							OSPF Configuration Example445
[RouterC] router id 3.3.3.3
[RouterC] ospf enable
[RouterC-ospf] interface ethernet 0
[RouterC-Ethernet0] ospf enable area 2
[RouterC-Ethernet0] interface serial 0
[RouterC-Serial0] ospf enable area 1
[RouterC-Serial0] quit
[RouterC] ospf
[RouterC-ospf] vlink peer-id 2.2.2.2 transit-area 1
Configuring OSPF Peer 
AuthenticationVerify peer authentication with simple text algorithm and MD5 algorithm. Simple 
text authentication is used when Router A and Router B exchange route updating 
and MD5 authentication is used when Router A and Router C exchange route 
updating. The Ethernet interface of Router A and that of Router B are in OSPF area 
0.The serial interface of Router A and that of Router B are both in area 1, 
configured with MD5 authentication.
Figure 150   Networking diagram of configuring OSPF peer authentication
To configure OSPF peer authentication:
1Configure Router A:
[RouterA] router id 1.1.1.1
[RouterA] ospf enable
[RouterA-ospf] interface ethernet 0
[RouterA-Ethernet0] ip address 192.1.1.1 255.255.255.0
[RouterA-Ethernet0] ospf enable area 0
[RouterA-Ethernet0] ospf authentication-mode simple 3Com
[RouterA-Ethernet0] interface serial 0
[RouterA-Serial0] ip address 193.1.1.1 255.255.255.0
[RouterA-Serial0] ospf enable area 1
[RouterA-Serial0] ospf authentication-mode md5 3Com 11
2Configure Router B:
[RouterB] router id 2.2.2.2
Area 0
Area 1E0 192. 1. 1. 2/ 24
S0 193. 1. 1. 1/ 24
MD5 authentication Simple authentication
0 0
0 02.2.2.2
1.1.1.1
3.3.3.3 Router ARouter B
Router C
E0 192. 1. 1. 1/ 24
S0 193.1.1.2/24 
						

							446CHAPTER 29: CONFIGURING OSPF
[RouterB] ospf enable 
[RouterB] interface ethernet 0
[RouterB-Ethernet0] ip address 192.1.1.2 255.255.255.0
[RouterB-Ethernet0] ospf enable area 0
[RouterB-Ethernet0] ospf authentication-mode simple 3Com
3Configure Router C:
[RouterC] router id 3.3.3.3
[RouterC] ospf enable 
[RouterC-ospf] interface serial 0
[RouterC-Serial0] ip address 193.1.1.2 255.255.255.0
[RouterC-Serial0] ospf enable area 1
[RouterC-Serial0] ospf authentication-mode md5 3Com 11
Troubleshooting an 
OSPF ConfigurationYou have configured OSPF as described previously, but router OSPF fails to run 
normally.
Perform the following procedures:
1Troubleshoot the local area: First check whether the protocol between the two 
directly connected routers is running normally. If the peer state machine between 
the two routers is in FULL status, it means the protocol is running normally. (Note 
that on broadcast network and NBMA network, the peer state machine between 
two DROther routers is not in FULL status but in 2 way status. DR, BDR and all 
other routers are in FULL status).
Use the display ospf peer command to view: 
[Router] display ospf peer
      Interface: 202.38.160.1    Area: 0.0.0.2
        Neighbors:
        RouterID: 2.2.2.2         Address: 202.38.160.2
        State:FULL  Mode: None    Priority: 0
        DR: 202.38.160.1  BDR: 202.38.160.1
        Last Hello: 14:04  Last Exchange: 0
        Authentication Sequence: a51dac
View OSPF information on the interface with the display ospf interface 
command.
■Check whether the physical connection and low layer protocol are running 
normally. If the opposite router cannot ping through the local router, it means 
that the physical connection and lower layer protocol are faulty.
■If the physical connection and lower layer protocol are normal, check the OSPF 
parameters configured on the interface. The parameters must be the same as 
those of the adjacent routers of this interface. The parameters include 
hellointerval, deadinterval and authentication. The area-id must be the same 
and the network segment and mask must be consistent (the network segment 
and mask of point-to-point and virtual link can be different).
■Check whether the deadinterval value is at least 4 times the hellointerval value 
on the same interface.
■If the network type is NBMA or point-to-multipoint, or the interface type is 
manually modified to point-to-point, use command 
ospf network-type p2p 
to manually specify the peer. In addition, when two routers are connected in