cisco hands-on experience


6. Implementing OSPF over NBMA

6.1 Understanding OSPF Network Types

6.1.1 Broadcast, Multi-Access Networks
• Example: Ethernet, Token Ring
• Single Operation Mode
• DR/BDR Election, 10 sec. Hellos, Dual Multicast Address
6.1.2 Point-to-point Networks
• Example: T/ Cas, ISDN BRI/PRI
• Single Operation Mode
• No DR/BDR, 10 sec. Hellos, Single Multicast Address
6.1.3 Non-Broadcast Multi-Access (NBMA) Networks
• Example: Frame Relay, ATM, X.25
• Five Modes of Operation

6.2 NBMA Topologies




6.3 OSPF over NBMA: Five Modes
1. Non-Broadcast (NBMA) – RFC Standard
2. Point-to-Multipoint – RFC Standard
3. Point-to-Point – Cisco Proprietary
4. Broadcast – Cisco Proprietary
5. Point-to-Mulitpoint, Non-Broadcast – Cisco Proprietary

6.3.1 Non-Broadcast Mode (.1)
• Default Mode for x.25, Frame Relay, ATM
• Neighbors statically configured
• Must be one subnet
• Acts like a LAN Environment
• DR/BDR elected (must have full connectivity)


6.3.2 Point-to-Multipoint Mode (.2)
• Fixes Issues with NBMA Networks
• Requires Single Subnet
• No DR/BDR elected
• Neighbors automatically Form



6.3.3 Point-to-Point – Cisco Proprietary (.3)
• Uses seperate Sub-Interfaces
• Requires Different Subnets
• No DR/BDR elected
• Neighbors automatically Form



6.3.4 Point-to-Mulitpoint, Non-Broadcast – Cisco Proprietary (.5)
• Fixes Issues with NBMA Networks
• Requires Single Subnet
• No DR/BDR elected
• Neighbors automatically form



6.4 Implementing OSPF over Multiple Network Types


6.4.1 Configuration of the Frame – Relay Switches
FRS1

interface Serial1/0
no ip address
encapsulation frame-relay
serial restart-delay 0
clock rate 64000
frame-relay lmi-type ansi
frame-relay intf-type dce
frame-relay route 102 interface Serial1/1 201
frame-relay route 103 interface Serial1/2 301

interface Serial1/1
no ip address
encapsulation frame-relay
serial restart-delay 0
clock rate 64000
frame-relay lmi-type ansi
frame-relay intf-type dce
frame-relay route 201 interface Serial1/0 102

interface Serial1/2
no ip address
encapsulation frame-relay
serial restart-delay 0
clock rate 64000
frame-relay lmi-type ansi
frame-relay intf-type dce
frame-relay route 301 interface Serial1/0 103

FRS2

interface Serial1/2
no ip address
encapsulation frame-relay
serial restart-delay 0
clock rate 64000
frame-relay lmi-type ansi
frame-relay intf-type dce
frame-relay route 204 interface Serial1/3 402

interface Serial1/3
no ip address
encapsulation frame-relay
serial restart-delay 0
clock rate 64000
frame-relay lmi-type ansi
frame-relay intf-type dce
frame-relay route 402 interface Serial1/2 204

FRS3

interface Serial1/3
no ip address
encapsulation frame-relay
serial restart-delay 0
clock rate 64000
frame-relay lmi-type ansi
frame-relay intf-type dce
frame-relay route 305 interface Serial1/4 503
frame-relay route 306 interface Serial1/5 603

interface Serial1/4
no ip address
encapsulation frame-relay
serial restart-delay 0
clock rate 64000
frame-relay lmi-type ansi
frame-relay intf-type dce
frame-relay route 503 interface Serial1/3 305

interface Serial1/5
no ip address
encapsulation frame-relay
serial restart-delay 0
clock rate 64000
frame-relay lmi-type ansi
frame-relay intf-type dce
frame-relay route 603 interface Serial1/3 306

6.4.2 Configuration for Non-Broadcast on Area 0
++++++++++++++ R1# +++++++++++++++

interface Loopback0
ip address 1.1.1.1 255.255.255.0
ip ospf network point-to-point

interface Serial1/0
no ip address
encapsulation frame-relay
serial restart-delay 0

interface Serial1/0.1 multipoint
ip address 10.12.3.1 255.255.255.0
frame-relay map ip 10.12.3.2 102 broadcast
frame-relay map ip 10.12.3.3 103 broadcast

R1#sh ip int brie
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 unassigned YES NVRAM administratively down down
FastEthernet0/1 unassigned YES NVRAM administratively down down
Serial1/0 unassigned YES NVRAM up up
Serial1/0.1 10.12.3.1 YES NVRAM up up
Serial1/1 unassigned YES NVRAM administratively down down
Serial1/2 unassigned YES NVRAM administratively down down
Serial1/3 unassigned YES NVRAM administratively down down
Serial1/4 unassigned YES NVRAM administratively down down
Serial1/5 unassigned YES NVRAM administratively down down
Serial1/6 unassigned YES NVRAM administratively down down
Serial1/7 unassigned YES NVRAM administratively down down
Loopback0 1.1.1.1 YES NVRAM up up

router ospf 1
router-id 1.1.1.1
log-adjacency-changes
network 1.1.1.1 0.0.0.0 area 0
network 10.12.3.0 0.0.0.255 area 0
neighbor 10.12.3.2
neighbor 10.12.3.3

R1#sh ip os int
Loopback0 is up, line protocol is up
Internet Address 1.1.1.1/24, Area 0
Process ID 1, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 1
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 1/1, flood queue length 0
Next 0×0(0)/0×0(0)
Last flood scan length is 0, maximum is 0
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
Serial1/0.1 is up, line protocol is up
Internet Address 10.12.3.1/24, Area 0
Process ID 1, Router ID 1.1.1.1, Network Type NON_BROADCAST, Cost: 64
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 1.1.1.1, Interface address 10.12.3.1
No backup designated router on this network
Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
oob-resync timeout 120
Hello due in 00:00:23
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 2/2, flood queue length 0
Next 0×0(0)/0×0(0)
Last flood scan length is 1, maximum is 2
Last flood scan time is 4 msec, maximum is 4 msec
Neighbor Count is 2, Adjacent neighbor count is 2
Adjacent with neighbor 2.2.2.2
Adjacent with neighbor 3.3.3.3
Suppress hello for 0 neighbor(s)

++++++++++++++ R2# +++++++++++++++

interface Loopback0
ip address 2.2.2.2 255.255.255.0
ip ospf network point-to-point

interface Serial1/1
no ip address
encapsulation frame-relay
serial restart-delay 0

interface Serial1/2
no ip address
encapsulation frame-relay
serial restart-delay 0

interface Serial1/1.1 multipoint
ip address 10.12.3.2 255.255.255.0
ip ospf priority 0
frame-relay map ip 10.12.3.3 201 broadcast
frame-relay map ip 10.12.3.1 201 broadcast

interface Serial1/2.1 point-to-point
ip address 10.24.0.2 255.255.255.0
frame-relay interface-dlci 204

router ospf 1
router-id 2.2.2.2
log-adjacency-changes
network 2.2.2.2 0.0.0.0 area 0
network 10.12.3.0 0.0.0.255 area 0
network 10.24.0.2 0.0.0.0 area 24

R2#sh ip int brie
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 unassigned YES NVRAM administratively down down
FastEthernet0/1 unassigned YES NVRAM administratively down down
Serial1/0 unassigned YES NVRAM administratively down down
Serial1/1 unassigned YES NVRAM up up
Serial1/1.1 10.12.3.2 YES NVRAM up up
Serial1/2 unassigned YES NVRAM up up
Serial1/2.1 10.24.0.2 YES NVRAM up up
Serial1/3 unassigned YES NVRAM administratively down down
Serial1/4 unassigned YES NVRAM administratively down down
Serial1/5 unassigned YES NVRAM administratively down down
Serial1/6 unassigned YES NVRAM administratively down down
Serial1/7 unassigned YES NVRAM administratively down down
Loopback0 2.2.2.2 YES NVRAM up up

R2#sh ip os int
Loopback0 is up, line protocol is up
Internet Address 2.2.2.2/24, Area 0
Process ID 1, Router ID 2.2.2.2, Network Type POINT_TO_POINT, Cost: 1
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 1/1, flood queue length 0
Next 0×0(0)/0×0(0)
Last flood scan length is 0, maximum is 0
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
Serial1/1.1 is up, line protocol is up
Internet Address 10.12.3.2/24, Area 0
Process ID 1, Router ID 2.2.2.2, Network Type NON_BROADCAST, Cost: 64
Transmit Delay is 1 sec, State DROTHER, Priority 0
Designated Router (ID) 1.1.1.1, Interface address 10.12.3.1
No backup designated router on this network
Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
oob-resync timeout 120
Hello due in 00:00:06
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 2/2, flood queue length 0
Next 0×0(0)/0×0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 4 msec, maximum is 4 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 1.1.1.1 (Designated Router)
Suppress hello for 0 neighbor(s)
Serial1/2.1 is up, line protocol is up
Internet Address 10.24.0.2/24, Area 24
Process ID 1, Router ID 2.2.2.2, Network Type POINT_TO_POINT, Cost: 64
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:06
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 1/3, flood queue length 0
Next 0×0(0)/0×0(0)
Last flood scan length is 4, maximum is 4
Last flood scan time is 0 msec, maximum is 4 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 4.4.4.4
Suppress hello for 0 neighbor(s)

++++++++++++++ R3# +++++++++++++++

interface Loopback0
ip address 3.3.3.3 255.255.255.0
ip ospf network point-to-point

interface Serial1/2
no ip address
encapsulation frame-relay
serial restart-delay 0

interface Serial1/3
no ip address
encapsulation frame-relay
serial restart-delay 0

interface Serial1/2.1 multipoint
ip address 10.12.3.3 255.255.255.0
ip ospf priority 0
frame-relay map ip 10.12.3.2 301 broadcast
frame-relay map ip 10.12.3.1 301 broadcast

interface Serial1/3.1 multipoint
ip address 10.35.6.3 255.255.255.0
ip ospf network point-to-multipoint
ip ospf hello-interval 10
frame-relay map ip 10.35.6.6 306 broadcast
frame-relay map ip 10.35.6.5 305 broadcast

router ospf 1
router-id 3.3.3.3
log-adjacency-changes
network 3.3.3.3 0.0.0.0 area 0
network 10.12.3.0 0.0.0.255 area 0
network 10.35.6.3 0.0.0.0 area 356

R3#sh ip int brie
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 unassigned YES NVRAM administratively down down
FastEthernet0/1 unassigned YES NVRAM administratively down down
Serial1/0 unassigned YES NVRAM administratively down down
Serial1/1 unassigned YES NVRAM administratively down down
Serial1/2 unassigned YES NVRAM up up
Serial1/2.1 10.12.3.3 YES NVRAM up up
Serial1/3 unassigned YES NVRAM up up
Serial1/3.1 10.35.6.3 YES NVRAM up up
Serial1/4 unassigned YES NVRAM administratively down down
Serial1/5 unassigned YES NVRAM administratively down down
Serial1/6 unassigned YES NVRAM administratively down down
Serial1/7 unassigned YES NVRAM administratively down down
Loopback0 3.3.3.3 YES NVRAM up up

R3# sh ip os int
Loopback0 is up, line protocol is up
Internet Address 3.3.3.3/24, Area 0
Process ID 1, Router ID 3.3.3.3, Network Type POINT_TO_POINT, Cost: 1
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 1/1, flood queue length 0
Next 0×0(0)/0×0(0)
Last flood scan length is 0, maximum is 0
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
Serial1/2.1 is up, line protocol is up
Internet Address 10.12.3.3/24, Area 0
Process ID 1, Router ID 3.3.3.3, Network Type NON_BROADCAST, Cost: 64
Transmit Delay is 1 sec, State DROTHER, Priority 0
Designated Router (ID) 1.1.1.1, Interface address 10.12.3.1
No backup designated router on this network
Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
oob-resync timeout 120
Hello due in 00:00:06
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 2/2, flood queue length 0
Next 0×0(0)/0×0(0)
Last flood scan length is 1, maximum is 2
Last flood scan time is 4 msec, maximum is 4 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 1.1.1.1 (Designated Router)
Suppress hello for 0 neighbor(s)
Serial1/3.1 is up, line protocol is up
Internet Address 10.35.6.3/24, Area 356
Process ID 1, Router ID 3.3.3.3, Network Type POINT_TO_MULTIPOINT, Cost: 64
Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:03
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 1/3, flood queue length 0
Next 0×0(0)/0×0(0)
Last flood scan length is 1, maximum is 5
Last flood scan time is 0 msec, maximum is 4 msec
Neighbor Count is 2, Adjacent neighbor count is 2
Adjacent with neighbor 6.6.6.6
Adjacent with neighbor 5.5.5.5
Suppress hello for 0 neighbor(s)

6.4.3 Configuration for Point-to-Point on Area 24
++++++++++++++ R4# +++++++++++++++

interface Loopback0
ip address 4.4.4.4 255.255.255.0
ip ospf network point-to-point

interface Serial1/3
no ip address
encapsulation frame-relay
serial restart-delay 0

interface Serial1/3.1 point-to-point
ip address 10.24.0.4 255.255.255.0
frame-relay interface-dlci 402

router ospf 1
router-id 4.4.4.4
log-adjacency-changes
network 4.4.4.4 0.0.0.0 area 24
network 10.24.0.0 0.0.0.255 area 24

R4#sh ip int brie
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 unassigned YES NVRAM administratively down down
FastEthernet0/1 unassigned YES NVRAM administratively down down
Serial1/0 unassigned YES NVRAM administratively down down
Serial1/1 unassigned YES NVRAM administratively down down
Serial1/2 unassigned YES NVRAM administratively down down
Serial1/3 unassigned YES NVRAM up up
Serial1/3.1 10.24.0.4 YES manual up up
Serial1/4 unassigned YES NVRAM administratively down down
Serial1/5 unassigned YES NVRAM administratively down down
Serial1/6 unassigned YES NVRAM administratively down down
Serial1/7 unassigned YES NVRAM administratively down down
Loopback0 4.4.4.4 YES manual up up

R4# sh ip os int
Loopback0 is up, line protocol is up
Internet Address 4.4.4.4/24, Area 24
Process ID 1, Router ID 4.4.4.4, Network Type POINT_TO_POINT, Cost: 1
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 2/2, flood queue length 0
Next 0×0(0)/0×0(0)
Last flood scan length is 0, maximum is 0
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
Serial1/3.1 is up, line protocol is up
Internet Address 10.24.0.4/24, Area 24
Process ID 1, Router ID 4.4.4.4, Network Type POINT_TO_POINT, Cost: 64
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:08
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 1/1, flood queue length 0
Next 0×0(0)/0×0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 4 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 2.2.2.2
Suppress hello for 0 neighbor(s)

6.4.4 Configuration for Hybrid Configuration on Area 356
++++++++++++++ R5# +++++++++++++++

interface Loopback0
ip address 5.5.5.5 255.255.255.0
ip ospf network point-to-point

interface Serial1/4
no ip address
encapsulation frame-relay
serial restart-delay 0

interface Serial1/4.1 point-to-point
ip address 10.35.6.5 255.255.255.0
frame-relay interface-dlci 503

router ospf 1
router-id 5.5.5.5
log-adjacency-changes
network 5.5.5.5 0.0.0.0 area 356
network 10.35.6.0 0.0.0.255 area 356

R5#sh ip int brie
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 unassigned YES NVRAM administratively down down
FastEthernet0/1 unassigned YES NVRAM administratively down down
Serial1/0 unassigned YES NVRAM administratively down down
Serial1/1 unassigned YES NVRAM administratively down down
Serial1/2 unassigned YES NVRAM administratively down down
Serial1/3 unassigned YES NVRAM up down
Serial1/3.1 unassigned YES manual deleted down
Serial1/4 unassigned YES NVRAM up up
Serial1/4.1 10.35.6.5 YES manual up up
Serial1/5 unassigned YES NVRAM administratively down down
Serial1/6 unassigned YES NVRAM administratively down down
Serial1/7 unassigned YES NVRAM administratively down down
Loopback0 5.5.5.5 YES manual up up

R5# sh ip os int
Loopback0 is up, line protocol is up
Internet Address 5.5.5.5/24, Area 356
Process ID 1, Router ID 5.5.5.5, Network Type POINT_TO_POINT, Cost: 1
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 1/1, flood queue length 0
Next 0×0(0)/0×0(0)
Last flood scan length is 0, maximum is 0
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
Serial1/4.1 is up, line protocol is up
Internet Address 10.35.6.5/24, Area 356
Process ID 1, Router ID 5.5.5.5, Network Type POINT_TO_POINT, Cost: 64
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:05
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 2/2, flood queue length 0
Next 0×0(0)/0×0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 4 msec, maximum is 4 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 3.3.3.3
Suppress hello for 0 neighbor(s)

++++++++++++++ R6# +++++++++++++++

interface Loopback0
ip address 6.6.6.6 255.255.255.0
ip ospf network point-to-point

interface Serial1/5
no ip address
encapsulation frame-relay
serial restart-delay 0

interface Serial1/5.1 point-to-point
ip address 10.35.6.6 255.255.255.0
frame-relay interface-dlci 603

router ospf 1
router-id 6.6.6.6
log-adjacency-changes
network 6.6.6.6 0.0.0.0 area 356
network 10.35.6.0 0.0.0.255 area 356

R6#sh ip int brie
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 unassigned YES NVRAM administratively down down
FastEthernet0/1 unassigned YES NVRAM administratively down down
Serial1/0 unassigned YES NVRAM administratively down down
Serial1/1 unassigned YES NVRAM administratively down down
Serial1/2 unassigned YES NVRAM administratively down down
Serial1/3 unassigned YES NVRAM administratively down down
Serial1/4 unassigned YES NVRAM administratively down down
Serial1/5 unassigned YES NVRAM up up
Serial1/5.1 10.35.6.6 YES manual up up
Serial1/6 unassigned YES NVRAM administratively down down
Serial1/7 unassigned YES NVRAM administratively down down
Loopback0 6.6.6.6 YES manual up up

R6#sh ip os int
Loopback0 is up, line protocol is up
Internet Address 6.6.6.6/24, Area 356
Process ID 1, Router ID 6.6.6.6, Network Type POINT_TO_POINT, Cost: 1
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 2/2, flood queue length 0
Next 0×0(0)/0×0(0)
Last flood scan length is 0, maximum is 0
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
Serial1/5.1 is up, line protocol is up
Internet Address 10.35.6.6/24, Area 356
Process ID 1, Router ID 6.6.6.6, Network Type POINT_TO_POINT, Cost: 64
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:07
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 1/1, flood queue length 0
Next 0×0(0)/0×0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 3.3.3.3
Suppress hello for 0 neighbor(s)