Troubleshooting Command Difference Between VPNv4 and VPNv6

Few last posts (IPv6 Internet In VRF Over MPLS Cloud, IPv6 Addresing Architecture, IPv6 From MPLS But Not In VRF) are almost describing about IPv6 deployment. But currently most of the service providers are providing vpnv4 and every network operation engineer is well known to the troubleshooting and provisioning process. In this post, I am depicting about the basic command line difference between the configuration and troubleshooting of VPNv4 and VPNv6. Except vrf configuration rest all commands are same, only we need to use IPv6 instead if IPv4.

IPv4 aVpnv4 Commands	Ipv6 and VPNv6 Commands
Global Commands
Ip routing	Ipv6 unicat-routing
Ip cef	Ipv6 cef
Interface Specific Commands
Ip address	Ipv6 address
Ip vrf forwarding MPLSVPN	Vrf forwarding MPLSVPN
VRF Specific Commands
Ip vrf MPLSVPN Rd 1:1 Route-target both 1:1	vrf definition ABC  rd 1:1  route-target export 1:1  route-target import 1:1  !  address-family ipv4  exit-address-family  !  address-family ipv6  exit-address-family
router bgp 1  address-family vpnv4  exit-address-family !  address-family ipv4  exit-address-family ! address-family ipv4 vrf MPLSVPN  exit-address-family	router bgp 1  address-family vpnv6  exit-address-family !  address-family ipv6  exit-address-family ! address-family ipv6 vrf MPLSVPN  exit-address-family
Static Vrf Route
Ip route vrf MPLSVPN	ipv6 route vrf MPLSVPN /
Show vrf commands
Show ip vrf interface	Show vrf ipv6 interface
Show ip interface brief	Show ipv6 interface brief
Troubleshooting Command
Show ip bgp vpnv4 all summary Show bgp vpnv4 all summary	Show ip bgp vpnv6 unicast all summary Show bgp vpnv6 unicast all summary
Show bgp vpnv4 all	Show bgp vpnv6 unicast all
Show ip bgp vpnv4 vrf MPLSVPN	Show bgp vpnv6 unicast vrf MPLSVPN
Show mpls forwarding-table vrf MPLSVPN detail	Show mpls forwarding-table vrf MPLSVPN detail
Show ip cef vrf MPLSVPN	Show ipv6 cef vrf MPLSVPN
Ping vrf MPLSVPN	Ping vrf MPLSVPN ipv6
Traceroute vrf MPLSVPN	Traceroute vrf MPLSVPN ipv6

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IPv6 Internet in VRF Over IPv4 MPLS Cloud

In my recent post of IPv6 over MPLS, I have shown the high level design of serving IPv6 internet from existing MPLS cloud. The crucial advantage of using this type of design is to bypass IGP for IPv6. Definitely this design is having its own limitations and challenges but we are parallelly working on those problems also. Before moving ahead make sure you have better understanding of Penultimate Hop Popping (PHP) and basic concept of accessing internet in vrf.
I have added a document with full configuration and results of serving IPv6 internet in VRF Over IPv4 MPLS cloud.

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OSPF External Routes Not Redistributing

I have seen many cases where external routes are not redistributing in OSPF or not getting install in the routing table. This happens when the next hop address is not reachable in the IGP. But the next question comes in mind that next hop address only plays role in BGP not in IGP. In IGP the next hop address of redistributed route is always ASBR address. We might be wrong this time; the immediate step is to check the “show ip ospf database external ”.

Output of show ip ospf database external 10.134.31.90
show ip ospf database external
OSPF Router with ID (10.10.10.1) (Process ID 1)
Type-5 AS External Link States
Routing Bit Set on this LSA
LS age: 298
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 10.134.31.90 (External Network Number )
Advertising Router: 10.10.10.2
LS Seq Number: 80003B51
Checksum: 0xF86
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 10.10.2.7

See the above output and value of forward address which 10.10.2.7. (See previous post which states the reason for non zero forward address). In normal condition this values must be 0.0.0.0 but we are receiving 10.10.2.7.

According to RFC 2328 section 16.4 which clearly states that “If the forwarding address is non-zero, look up the forwarding address in the routing table. The matching routing table entry must specify an intra-area or inter-area path; if no such path exists, do nothing with the LSA and consider the next in the list”.

This means if either the forward address is not reachable in the IGP or it is coming via external route also. This is the reason for not installing the static route in IGP.


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