This topic is to discuss the following lesson:
I noticed nhrp redirect is missing on the Hub DVMP configuration. Is this optional for DMVPN phase 3?
Hi Nagi,
Good call! You are 100% correct. DMVPN phase 3 requires “ip nhrp redirect” to be on the hub–in fact the presence of “ip nhrp redirect” on the hub and “ip nhrp shortcut” on the spokes are the key differences in configuration between phase 3 and other phases.
I suspect Rene just left that out by accident in the main body of the article. You will notice, however, at the bottom in the “tabbed” configuration section for the Hub, it is there.
It has been fixed now, thanks for sharing!
Hi,
Do we have this kind of tutorial with VRF ; customer vrf and transport vrf ?
Thanks,
Gk
Do we always have to advertise default route on HUB ?
Otherwise there is no way that spokes learn routes each other ?
Gopal,
You don’t have to advertise a default route from the Hub. However, having the ability to do this AND have the spokes be able to communicate directly with each other are the hallmark features of Phase 3 as opposed to any other phase.
The reason this is beneficial is that it keeps the number of routes on the spokes to a minimum (in phase 2 you would have to have [N * (N-1) / 2] number of routes per spoke, where N = number of spokes), and when spoke to spoke traffic needs to happen, the hub is left out of the data plane.
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Hi Andrew,
Thanks.
Do we have any examples on Dual HUB along with links to two service providers from each HUB. Same thing from spoke router as well.
Thanks Rene
Hello Rene,
I have one quick question regarding the BGP configuration in DMVPN phase 3. In Phase 3 BGP configuration, the Hub router is advertising a default route to the spokes through BGP. Let’s say the spoke routers already have default routes to the ISP for the local users’ internet access. In this scenario, how can the Hub router advertise default route to the spokes? Thank you so much in advance.
That is indeed a chicken and egg problem. If you use a default route outbound towards your ISP, then you can’t use another default route for your DMVPN routing. You should use more specific routes for DMVPN.
Hello Rene,
I hope you’re doing well.
I want to know why we need config muticast dynamic for DMVPN?
BR,
Ulrich
Hello Ulrich,
Connections are initiated from the spoke routers to the hub, and the hub doesn’t know beforehand what the IP addresses of the spoke routers are.
Theip nhrp map multicast dynamic command tells NHRP to automatically add routers to the multicast NHRP mappings.
You can see in the configuration of the spoke routers that we have a static multicast entry with the IP address of the hub router on them.
Rene
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Just wondering why you use the route-map for the neighbours outbound?
If you use the “network 0.0.0.0 mask 0.0.0.0” in the BGP routing process, why do you also need to create a route-map specifying the same thing again?
Hello Chris,
Good question. If you use eBGP and the same AS number on the spoke routers then the route-map isn’t really needed since the spoke routers will deny prefixes with their own AS number. On the other hand, the hub will advertise those prefixes so a route-map isn’t a bad idea…it ensures that we really only advertise the default route.
If you use eBGP and different AS numbers on the spoke routers, the route-map is a good idea.
With iBGP, it’s also not really needed since because of split horizon, the hub won’t advertise a prefix from one spoke to another. The route-map does prevent advertising a prefix in case the hub would learn some prefixes from another BGP router…perhaps some eBGP router in another AS that is connected to the hub.
Rene
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im having trouble seeing my spoke network. for example on spoke 1 i can see spoke two network in my routing table but from spoke 2 im unable to see my spoke 1 network
configuration lab from gns3:
hostname MIAMI hub
!
int tun0
Des Miami HUB
ip address 10.100.252.1 255.255.255.0
no ip redirects
ip mtu 1400
ip nhrp map multicast dynamic
ip nhrp network-id 100
ip nhrp redirect
ip nhrp shortcut
ip tcp adjust-mss 1360
no ip split-horizon
tunnel source FastEthernet0/0
tunnel mode gre multipoint
exit
!
interface Loopback0
ip address 10.100.0.4 255.255.255.255
!
interface FastEthernet0/0
ip address 198.36.220.36 255.255.255.224
duplex auto
speed auto
!
router bgp 65000
no synchronization
bgp log-neighbor-changes
network 0.0.0.0
network 10.100.0.4 mask 255.255.255.255
network 10.100.252.6 remote-as 65020
neighbor 10.100.252.114 remote-as 65114
no auto-summary
!
ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 198.136.220.33
Homedale spoke 1:
config t
!
hostname HOMEDALE
!
interface Loopback0
ip address 10.6.0.2 255.255.255.255
!
interface Tunnel0
DES Link to Miami Hub
ip address 10.100.252.6 255.255.255.0
ip mtu 1400
ip nhrp map 10.100.252.1 198.136.220.36
ip nhrp map multicast 198.136.220.36
ip nhrp network-id 100
ip nhrp nhs 10.100.252.1
ip nhrp redirect
ip nhrp shortcut
ip tcp adjust-mss 1360
tunnel source FastEthernet0/0
tunnel mode gre multipoint
exit
!
!
interface FastEthernet0/0
ip address 204.114.124.36 255.255.255.240
duplex auto
speed auto
!
!
router bgp 65020
no synchronization
bgp log-neighbor-changes
network 10.6.0.2 mask 255.255.255.255
neighbor 10.100.252.1 remote-as 65000
neighbor 10.100.252.1 timers 7 21
neighbor 10.102.252.1 remote-as 65016
neighbor 10.102.252.1 timers 7 21
no auto-summary
!
ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 204.114.124.33
ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 204.114.124.33
spoke 2
Tamp
!
interface Loopback0
ip address 10.114.0.2 255.255.255.255
!
interface Tunnel0
Des link to Miami Hub
ip address 10.100.252.114 255.255.255.0
ip mtu 1400
ip nhrp map 10.100.252.1 198.136.220.36
ip nhrp map multicast 198.136.220.36
ip nhrp network-id 100
ip nhrp nhs 10.100.252.1
ip nhrp redirect
ip nhrp shortcut
ip tcp adjust-mss 1360
tunnel source FastEthernet0/0
tunnel mode gre multipoint
exit
!
router bgp 65114
no synchronization
bgp router-id 10.114.0.2
bgp log-neighbor-changes
network 10.114.0.2 mask 255.255.255.255
neighbor 10.100.252.1 remote-as 65000
neighbor 10.100.252.1 timers 7 21
neighbor 10.102.252.1 remote-as 65016
neighbor 10.102.252.1 timers 7 21
no auto-summary
!
ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 64.112.157.233
internet#sh run
Building configuration...
Current configuration : 1234 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname internet
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 5
no ip icmp rate-limit unreachable
ip cef
!
!
!
!
no ip domain lookup
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
archive
log config
hidekeys
!
!
!
!
ip tcp synwait-time 5
!
!
!
!
interface FastEthernet0/0
description ISP to SMY
ip address 64.238.201.94 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
description ISP to TAMPA
ip address 64.112.157.233 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet1/0
description ISP to Miami
ip address 198.136.220.33 255.255.255.224
duplex auto
speed auto
!
interface FastEthernet2/0
description ISP to HOMDALES
ip address 204.114.124.33 255.255.255.0
duplex auto
speed auto
!
ip forward-protocol nd
!
!
no ip http server
no ip http secure-server
!
no cdp log mismatch duplex
!
!
!
!
!
!
control-plane
!
!
!
!
!
!
!
!
!
!
line con 0
exec-timeout 0 0
privilege level 15
logging synchronous
line aux 0
exec-timeout 0 0
privilege level 15
logging synchronous
line vty 0 4
login
!
!
endHello Jeffery,
First thing I notice, you only have one neighbor command on your hub?
neighbor 10.100.252.114 remote-as 65114Rene
Rene I have both neighbor 10.100.252.114 remote-as 65114 and neighbor 10.100.252.6 remote-as 65020 on the miami hub i didn’t realize i uploaded the wrong configs for the hub but this is my most recent configs sorry about that
Miami#sh running-config
Building configuration...
Current configuration : 2377 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Miami
!
ip cef
!
no ip domain lookup
!
interface Loopback0
ip address 10.100.0.4 255.255.255.255
!
interface Loopback1
ip address 10.100.254.22 255.255.255.248
!
interface Tunnel0
description Miami HUB
no ip address
no ip redirects
ip mtu 1400
ip nhrp map multicast dynamic
ip nhrp network-id 100
ip nhrp shortcut
ip nhrp redirect
ip tcp adjust-mss 1360
no ip split-horizon
tunnel source FastEthernet0/0
tunnel mode gre multipoint
!
interface Tunnel1
ip address 10.100.252.1 255.255.255.0
no ip redirects
ip mtu 1400
ip nhrp map multicast dynamic
ip nhrp network-id 102
ip tcp adjust-mss 1360
tunnel source FastEthernet0/0
tunnel mode gre multipoint
!
interface FastEthernet0/0
ip address 198.136.220.36 255.255.255.224
duplex auto
speed auto
!
router bgp 65000
no synchronization
bgp log-neighbor-changes
network 0.0.0.0
network 10.100.0.4 mask 255.255.255.255
neighbor 10.100.252.6 remote-as 65020
neighbor 10.100.252.6 timers 7 21
neighbor 10.100.252.114 remote-as 65114
neighbor 10.100.252.114 timers 7 21
no auto-summary
!
ip route 0.0.0.0 0.0.0.0 198.136.220.33
!
end