L2TPv3 (Layer 2 Tunnel Protocol Version 3) é um protocolo usado para criar túneis de camada 2 sobre uma rede IP. Tem como objetivo principal transportar diferentes tipos de tráfego de camada 2 como Ethernet, Frame Relay, ATM, entre outros. Neste artigo veremos como implementar L2TPv3 entre os routers RT2 e RT4, simulando a rede de uma provedora. Ao final do artigo, os routers RT1 e RT5 formarão adjacência EIGRP como se estivessem na mesma LAN. Mãos à obra.
RT1
en
conf t
line con 0
logg s
exec-t 0 0
privil level 15
no ip domain lo
int e0/0
ip add 10.0.15.1 255.255.255.0
no shut
router eigrp 15
network 10.0.15.1 0.0.0.0
host RT1
no cdp ad
no ser tim
do wr
RT2
en
conf t
line con 0
logg s
exec-t 0 0
privil level 15
no ip domain lo
int e0/0
no shut
int e0/1
ip add 10.0.23.2 255.255.255.0
no shut
router ospf 1
net 10.0.23.2 0.0.0.0 area 0
host RT2
no cdp ad
no ser tim
do wr
RT3
en
conf t
line con 0
logg s
exec-t 0 0
privil level 15
no ip domain lo
int e0/0
ip add 10.0.23.3 255.255.255.0
no shut
int e0/1
ip add 10.0.34.3 255.255.255.0
no shut
router ospf 1
net 10.0.23.3 0.0.0.0 area 0
net 10.0.34.3 0.0.0.0 area 0
host RT3
no cdp ad
no ser tim
do wr
RT4
en
conf t
line con 0
logg s
exec-t 0 0
privil level 15
no ip domain lo
int e0/0
no shut
int e0/1
ip add 10.0.34.4 255.255.255.0
no shut
int lo0
ip add 4.4.4.4 255.255.255.255
router ospf 1
net 10.0.34.4 0.0.0.0 area 0
host RT4
no cdp ad
no ser tim
do wr
RT5
en
conf t
line con 0
logg s
exec-t 0 0
privil level 15
no ip domain lo
int e0/0
ip add 10.0.15.5 255.255.255.0
no shut
router eigrp 15
network 10.0.15.5 0.0.0.0
host RT5
no cdp ad
no ser tim
do wr
Esta configuração serve somente de preparação para a configuração de L2TPv3. É boa prática fazer a configuração em partes e garantir que a cada passo, existe conectividade entre os equipamentos necessários. Antes de avançar, garanta que RT2 consegue fazer ping à interface E0/1 de RT4.
RT2
Podemos seguir com a configuração de L2TPv3.
RT2
pseudowire-class PW_R2R4
encapsulation l2tpv3
ip local interface Ethernet0/1
!
interface Ethernet0/0
no ip address
xconnect 10.0.34.4 24 encapsulation l2tpv3 pw-class PW_R2R4
!
RT4
pseudowire-class PW_R2R4
encapsulation l2tpv3
ip local interface Ethernet0/1
!
interface Ethernet0/0
no ip address
xconnect 10.0.23.2 24 encapsulation l2tpv3 pw-class PW_R2R4
!
Após configurar L2TPv3 do lado do RT4, o circuito estará up. Podemos usar os comandos abaixo para validar.
RT4#show l2tun tunnel all
L2TP Tunnel Information Total tunnels 1 sessions 1
Tunnel id 2454351502 is up, remote id is 3397189275, 1 active sessions
Locally initiated tunnel
Tunnel state is established, time since change 00:25:44
Tunnel transport is IP (115)
Remote tunnel name is RT2
Internet Address 10.0.23.2, port 0
Local tunnel name is RT4
Internet Address 10.0.34.4, port 0
L2TP class for tunnel is l2tp_default_class
Counters, taking last clear into account:
523 packets sent, 521 received
44176 bytes sent, 44346 received
Last clearing of counters never
Counters, ignoring last clear:
523 packets sent, 521 received
44176 bytes sent, 44346 received
Control Ns 29, Nr 28
Local RWS 1024 (default), Remote RWS 1024
Control channel Congestion Control is disabled
Tunnel PMTU checking disabled
Retransmission time 1, max 1 seconds
Unsent queuesize 0, max 0
Resend queuesize 0, max 2
Total resends 0, ZLB ACKs sent 26
Total out-of-order dropped pkts 0
Total out-of-order reorder pkts 0
Total peer authentication failures 0
Current no session pak queue check 0 of 5
Retransmit time distribution: 0 0 0 0 0 0 0 0 0
Control message authentication is disabled
RT4#show l2tp session
L2TP Session Information Total tunnels 1 sessions 1
LocID RemID TunID Username, Intf/ State Last Chg Uniq ID
Vcid, Circuit
1379409031 921026028 2454351502 24, Et0/0 est 00:28:20 0
RT4#show l2tp session all
L2TP Session Information Total tunnels 1 sessions 1
Session id 1379409031 is up, logical session id 32787, tunnel id 2454351502
Remote session id is 921026028, remote tunnel id 3397189275
Locally initiated session
Unique ID is 0
Session Layer 2 circuit, type is Ethernet, name is Ethernet0/0
Session vcid is 24
Circuit state is UP
Local circuit state is UP
Remote circuit state is UP
Call serial number is 1021600001
Remote tunnel name is RT2
Internet address is 10.0.23.2
Local tunnel name is RT4
Internet address is 10.0.34.4
IP protocol 115
Session is L2TP signaled
Session state is established, time since change 00:28:41
582 Packets sent, 581 received
49126 Bytes sent, 49626 received
Last clearing of counters never
Counters, ignoring last clear:
582 Packets sent, 581 received
49126 Bytes sent, 49626 received
Receive packets dropped:
out-of-order: 0
other: 0
total: 0
Send packets dropped:
exceeded session MTU: 0
other: 0
total: 0
DF bit off, ToS reflect disabled, ToS value 0, TTL value 255
Sending UDP checksums are disabled
Received UDP checksums are verified
No session cookie information available
FS cached header information:
encap size = 24 bytes
45000014 00000000 ff736e71 0a002204
0a001702 36e5bdec
Sequencing is off
Conditional debugging is disabled
SSM switch id is 4110, SSM segment id is 8214
Também podemos validar que os routers RT1 e RT5 estabeleceram adjacência EIGRP com sucesso.
RT1#show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(15)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 10.0.15.5 Et0/0 12 00:31:17 1 3000 0 1
L2TPv3 é uma tecnologia poderosa para criar túneis de camada 2 através de redes IP, suportando uma ampla gama de protocolos e oferecendo flexibilidade e escalabilidade em ambientes de rede complexos.