DMVPN allowas-in
Env
Physical: 169.254.100.0/24
Tunnel1: 155.1.0.0/24
Loopback0: 150.1.x.x/32
config
iosv-5(Hub)
R5#sh run | s Tunnel1|router bgp|route-map|prefix-list
interface Tunnel1
ip address 155.1.0.5 255.255.255.0
no ip redirects
ip nhrp authentication PRIMARY
ip nhrp network-id 1
ip nhrp redirect
tunnel source 169.254.100.5
tunnel mode gre multipoint
tunnel key 1
router bgp 100
bgp log-neighbor-changes
bgp listen range 155.1.0.0/24 peer-group spoke1
neighbor spoke1 peer-group
neighbor spoke1 remote-as 200
neighbor spoke1 update-source Tunnel1
neighbor spoke1 default-originate
neighbor spoke1 route-map DEFAULT out
ip prefix-list PRE seq 5 permit 0.0.0.0/0
route-map DEFAULT permit 10
match ip address prefix-list PREiosv-1(Spoke)
R1#sh run | s Tunnel1|router bgp
interface Tunnel1
ip address 155.1.0.1 255.255.255.0
no ip redirects
ip nhrp authentication PRIMARY
ip nhrp map multicast 169.254.100.5
ip nhrp map 155.1.0.5 169.254.100.5
ip nhrp network-id 1
ip nhrp nhs 155.1.0.5
ip nhrp redirect
tunnel source 169.254.100.1
tunnel mode gre multipoint
tunnel key 1
router bgp 200
bgp log-neighbor-changes
network 150.1.1.1 mask 255.255.255.255
neighbor 155.1.0.5 remote-as 100
neighbor 155.1.0.5 update-source Tunnel1iosv-2(Spoke)
R2#sh run | s Tunnel1|router bgp
interface Tunnel1
ip address 155.1.0.2 255.255.255.0
no ip redirects
ip nhrp authentication PRIMARY
ip nhrp map multicast 169.254.100.5
ip nhrp map 155.1.0.5 169.254.100.5
ip nhrp network-id 1
ip nhrp nhs 155.1.0.5
ip nhrp redirect
tunnel source 169.254.100.2
tunnel mode gre multipoint
tunnel key 1
router bgp 200
bgp log-neighbor-changes
network 150.1.2.2 mask 255.255.255.255
neighbor 155.1.0.5 remote-as 100
neighbor 155.1.0.5 update-source Tunnel1Verifying
show dmvpn
R5#sh dm | b Interface
Interface: Tunnel1, IPv4 NHRP Details
Type:Hub, NHRP Peers:2,
# Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb
----- --------------- --------------- ----- -------- -----
1 169.254.100.1 155.1.0.1 UP 00:24:34 D
1 169.254.100.2 155.1.0.2 UP 00:23:48 D
R1#sh dm | b Interface
Interface: Tunnel1, IPv4 NHRP Details
Type:Spoke, NHRP Peers:1,
# Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb
----- --------------- --------------- ----- -------- -----
1 169.254.100.5 155.1.0.5 UP 00:13:46 S
R2#sh dm | b Interface
Interface: Tunnel1, IPv4 NHRP Details
Type:Spoke, NHRP Peers:1,
# Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb
----- --------------- --------------- ----- -------- -----
1 169.254.100.5 155.1.0.5 UP 00:26:03 Sshow ip route
In this case, R5`s routing table is not important, so it`s skipped.
R1#sh ip ro | b Gate
Gateway of last resort is 155.1.0.5 to network 0.0.0.0
B* 0.0.0.0/0 [20/0] via 155.1.0.5, 00:09:38
150.1.0.0/32 is subnetted, 1 subnets
C 150.1.1.1 is directly connected, Loopback0
150.2.0.0/32 is subnetted, 1 subnets
C 150.2.1.1 is directly connected, Loopback2
155.1.0.0/16 is variably subnetted, 4 subnets, 2 masks
C 155.1.0.0/24 is directly connected, Tunnel1
L 155.1.0.1/32 is directly connected, Tunnel1
169.254.0.0/16 is variably subnetted, 2 subnets, 2 masks
C 169.254.100.0/24 is directly connected, GigabitEthernet0/0
L 169.254.100.1/32 is directly connected, GigabitEthernet0/0
R2#sh ip ro | b Gate
Gateway of last resort is 155.1.0.5 to network 0.0.0.0
B* 0.0.0.0/0 [20/0] via 155.1.0.5, 00:09:49
150.1.0.0/32 is subnetted, 1 subnets
C 150.1.2.2 is directly connected, Loopback0
150.2.0.0/32 is subnetted, 1 subnets
C 150.2.2.2 is directly connected, Loopback2
155.1.0.0/16 is variably subnetted, 2 subnets, 2 masks
C 155.1.0.0/24 is directly connected, Tunnel1
L 155.1.0.2/32 is directly connected, Tunnel1
169.254.0.0/16 is variably subnetted, 2 subnets, 2 masks
C 169.254.100.0/24 is directly connected, GigabitEthernet0/0
L 169.254.100.2/32 is directly connected, GigabitEthernet0/02 times traceroute & show commands
R1#traceroute 150.1.2.2
Type escape sequence to abort.
Tracing the route to 150.1.2.2
VRF info: (vrf in name/id, vrf out name/id)
1 155.1.0.5 [AS 100] 4 msec 3 msec 2 msec
2 155.1.0.2 [AS 100] 7 msec 3 msec 6 msec
R1#traceroute 150.1.2.2
Type escape sequence to abort.
Tracing the route to 150.1.2.2
VRF info: (vrf in name/id, vrf out name/id)
1 155.1.0.2 [AS 100] 3 msec 3 msec 2 msec
R1#sh dm | b Interface
Interface: Tunnel1, IPv4 NHRP Details
Type:Spoke, NHRP Peers:2,
# Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb
----- --------------- --------------- ----- -------- -----
2 169.254.100.2 155.1.0.2 UP 00:00:57 DT1
155.1.0.2 UP 00:00:57 DT1
1 169.254.100.5 155.1.0.5 UP 00:19:48 S
R1#sh ip ro | b Gate
Gateway of last resort is 155.1.0.5 to network 0.0.0.0
B* 0.0.0.0/0 [20/0] via 155.1.0.5, 00:12:58
150.1.0.0/32 is subnetted, 2 subnets
C 150.1.1.1 is directly connected, Loopback0
H 150.1.2.2 [250/255] via 155.1.0.2, 00:01:15, Tunnel1
150.2.0.0/32 is subnetted, 1 subnets
C 150.2.1.1 is directly connected, Loopback2
155.1.0.0/16 is variably subnetted, 5 subnets, 2 masks
C 155.1.0.0/24 is directly connected, Tunnel1
L 155.1.0.1/32 is directly connected, Tunnel1
H 155.1.0.2/32 is directly connected, 00:01:15, Tunnel1
C 155.1.146.0/24 is directly connected, GigabitEthernet0/2
L 155.1.146.1/32 is directly connected, GigabitEthernet0/2
169.254.0.0/16 is variably subnetted, 2 subnets, 2 masks
C 169.254.100.0/24 is directly connected, GigabitEthernet0/0
L 169.254.100.1/32 is directly connected, GigabitEthernet0/0show ip bgp(Main Theme)
If they were in MPLS topology(iosv-1&2 were CE), they would have to be configured "allowas-in" because both of routers are in same Autonomous-system, 200.
However, in this DMVPN topology, they do not need the allowas-in command, because Hub(iosv-5) originates and advertises a default-route to Spokes, and it suppresses other prefixes.
R1#sh ip bgp
BGP table version is 5, local router ID is 150.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
x best-external, a additional-path, c RIB-compressed,
t secondary path,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found
Network Next Hop Metric LocPrf Weight Path
*> 0.0.0.0 155.1.0.5 0 100 i
*> 150.1.1.1/32 0.0.0.0 0 32768 iTherefore, the "show ip bgp" command on iosv-1 shows that the default-route which is advertised by Hub(iosv-5) has "100 i" AS_PATH attributes with no 200.
Reference
CCIE Enterprise Infrastructure Foundation, 2nd Edition
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