[c-nsp] Problems with multipoint GRE / NHRP

[Daniel Roesen]

Hi,

I'm trying to set up a GRE tunnel with roadwarrior support (one endpoint
with dynamic IP).

R1: hub router, 12.3(11)T2
R2: spoke router, with dynamic IP on Dialer4, 12.3(8)T6

Hub router config:
==================
interface Tunnel12
 ip address 10.0.12.1 255.255.255.252
 no ip redirects
 ip mtu 1500
 ip router isis
 ip pim sparse-mode
 ip nhrp authentication xxx
 ip nhrp map multicast dynamic
 ip nhrp network-id 99
 ip nhrp holdtime 1000
 ip nhrp server-only
...
 tunnel source FastEthernet0/1
 tunnel mode gre multipoint
 tunnel key xxx

Spoke router config:
====================
interface Tunnel12
 ip address 10.0.12.2 255.255.255.252
 no ip redirects
 ip mtu 1500
 ip router isis
 ip pim sparse-mode
 ip nhrp authentication xxx
 ip nhrp map multicast dynamic
 ip nhrp map 10.0.12.1 192.168.22.22
 ip nhrp map multicast 192.168.22.22
 ip nhrp network-id 99
 ip nhrp holdtime 1000
 ip nhrp nhs 10.0.12.1
 tunnel source Dialer4
 tunnel mode gre multipoint
 tunnel key xxx

R2 sends NHRP registration request to R1, R1 accepts and replies.
NHRP debugging on R2 never shows the reply reception, although R1
correctly addresses it to R2's Dialer4 IP address.

Debugging on R2 showing the NHRP Reg Request:

NHRP: Setting retrans delay to 64 for nhs  dst 10.0.12.1
NHRP: Attempting to send packet via DEST 10.0.12.1
NHRP: Encapsulation succeeded.  Tunnel IP addr 192.168.22.22
NHRP: Send Registration Request via Tunnel12 vrf 0, packet size: 81
 src: 10.0.12.2, dst: 10.0.12.1
 (F) afn: IPv4(1), type: IP(800), hop: 255, ver: 1
     shtl: 4(NSAP), sstl: 0(NSAP)
 (M) flags: "unique", reqid: 17
     src NBMA: $R2Dialer4IP
     src protocol: 10.0.12.2, dst protocol: 10.0.12.1
 (C-1) code: no error(0)
       prefix: 255, mtu: 1514, hd_time: 1000
       addr_len: 0(NSAP), subaddr_len: 0(NSAP), proto_len: 0, pref: 0
NHRP: 81 bytes out Tunnel12

Debug log on R1 showing reception of the request and sending of reply:

NHRP: Receive Registration Request via Tunnel12 vrf 0, packet size: 81
 (F) afn: IPv4(1), type: IP(800), hop: 255, ver: 1
     shtl: 4(NSAP), sstl: 0(NSAP)
 (M) flags: "unique", reqid: 17
     src NBMA: $R2Dialer4IP
     src protocol: 10.0.12.2, dst protocol: 10.0.12.1
 (C-1) code: no error(0)
       prefix: 255, mtu: 1514, hd_time: 1000
       addr_len: 0(NSAP), subaddr_len: 0(NSAP), proto_len: 0, pref: 0
NHRP: netid_in = 99, to_us = 1
NHRP: NAT-check: matched destination address $R2Dialer4IP
NHRP: Cache update for target 10.0.12.2/32 next-hop 10.0.12.2
           $R2Dialer4IP
NHRP: Converted internal dynamic cache entry for 10.0.12.2/32 interface Tunnel12 to external
NHRP: Attempting to send packet via DEST 10.0.12.2
NHRP: Encapsulation succeeded.  Tunnel IP addr $R2Dialer4IP
NHRP: Send Registration Reply via Tunnel12 vrf 0, packet size: 101
 src: 10.0.12.1, dst: 10.0.12.2
 (F) afn: IPv4(1), type: IP(800), hop: 255, ver: 1
     shtl: 4(NSAP), sstl: 0(NSAP)
 (M) flags: "unique", reqid: 17
     src NBMA: $R2Dialer4IP
     src protocol: 10.0.12.2, dst protocol: 10.0.12.1
 (C-1) code: no error(0)
       prefix: 255, mtu: 1514, hd_time: 1000
       addr_len: 0(NSAP), subaddr_len: 0(NSAP), proto_len: 0, pref: 0
NHRP: 101 bytes out Tunnel12

R2 never seems to receive the reply. Bug? Unfortunately, can't easily
sniff the traffic to see wether the reply is actually put on the wire
by R1 towards R2.

When reconfiguring R2 from "tunnel mode gre multipoint" to "tunnel mode
gre ip" and specificing R1 as tunnel destination, NHRP registration
succeeds. But then I have the problem that R2 tries to send P2P IIH
instead of LAN IIH, and thus IS-IS adjacency not comming up as R1
rejects the P2P IIHs. PIM works fine (at least brings up adjacency)
though.

Any insight?


Best regards,
Daniel

-- 
CLUE-RIPE -- Jabber: dr at cluenet.de -- dr at IRCnet -- PGP: 0xA85C8AA0