E-Line is a point-to-point Ethernet service between two customer sites. On an MPLS network the same service is called VPWS: each PE connects the customer-facing port to a pseudowire. The two PEs exchange the pseudowire labels over a targeted LDP session. The pseudowire rides whatever LSP the PE has to the other PE: LDP, RSVP-TE or BGP labeled unicast.
This stage builds one E-Line between CustB-Hub on A-PE1 and CustB-Spk1 on A-PE2, with VC ID 2011. This is the pseudowire on A-PE1 after the stage was configured:
A-PE1#show mpls l2transport vc 2011 detail
Local interface: Gi5 up, line protocol up, Eth VLAN 11 up
Interworking type is Ethernet
Destination address: 10.1.0.6, VC ID: 2011, VC status: up
Output interface: Tu10, imposed label stack {1112 1614}
Preferred path: not configured
Default path: active
Next hop: point2point
Create time: 00:14:39, last status change time: 00:13:21
Last label FSM state change time: 00:13:21
Signaling protocol: LDP, peer 10.1.0.6:0 up
Targeted Hello: 10.1.0.5(LDP Id) -> 10.1.0.6, LDP is UP
Graceful restart: not configured and not enabled
Non stop routing: not configured and not enabled
Status TLV support (local/remote) : enabled/supported
LDP route watch : enabled
Label/status state machine : established, LruRru
Last local dataplane status rcvd: No fault
Last BFD dataplane status rcvd: Not sent
Last BFD peer monitor status rcvd: No fault
Last local AC circuit status rcvd: No fault
Last local AC circuit status sent: No fault
Last local PW i/f circ status rcvd: No fault
Last local LDP TLV status sent: No fault
Last remote LDP TLV status rcvd: No fault
Last remote LDP ADJ status rcvd: No fault
MPLS VC labels: local 1517, remote 1614
Group ID: local 10, remote 10
MTU: local 1500, remote 1500
Remote interface description: VPWS E-Line VC 2011 -> CustB-Spk1<->Hub
Sequencing: receive disabled, send disabled
Control Word: On
SSO Descriptor: 10.1.0.6/2011, local label: 1517
Dataplane:
SSM segment/switch IDs: 4108/4105 (used), PWID: 1
VC statistics:
transit packet totals: receive 24, send 22
transit byte totals: receive 3234, send 2746
transit packet drops: receive 0, seq error 0, send 0A-PE1 sends the pseudowire into Tunnel10 with two labels: 1112 is A-P1’s label for Tunnel10, and 1614 is the VC label A-PE2 advertised. No preferred path is configured, so the pseudowire follows the route to A-PE2’s loopback 10.1.0.6.
In the TE stage, autoroute destination on Tunnel10 installed a static route to 10.1.0.6/32 through the tunnel.
Topology file: topology.clab.yml · Addressing: ipam.md · Stage configs, 4 nodes (the two PEs and the two CustB CEs): stage_configs/lab02-s3a-spa-vpws/
Gi5 as an EVC Trunk
Each CustB CE has a single link to its PE, and the lab runs two L2 services for CustB on these two PEs. Gi5 on both PEs is an 802.1Q trunk with no IP address and one service instance per service: VLAN 11 for this E-Line, VLAN 12 left for an EVPN-ELAN (will be described later in the other lab).
interface GigabitEthernet5
description CustB multi-service UNI -- VLAN11 VPWS VC2011 | VLAN12 EVPN(S3B,reserved)
no ip address
no ipv6 address 2001:DB8:1:22::1/64
no keepalive
service instance 11 ethernet
description VPWS E-Line VC 2011 -> CustB-Hub<->Spk1
encapsulation dot1q 11
rewrite ingress tag pop 1 symmetric
xconnect 10.1.0.6 2011 encapsulation mpls pw-class VPWS_CB_CWService instance 11 takes frames tagged 11, and its xconnect points to A-PE2’s loopback 10.1.0.6. rewrite ingress tag pop 1 symmetric removes tag 11 from frames coming from the CE and pushes it back on frames going to the CE. A-PE2 has the same service instance toward 10.1.0.5.
CustB-Hub sends VLAN 11 from a dot1Q subinterface:
interface Ethernet0/1.11
description VPWS E-Line (VLAN 11) -> CustB-Spk1
encapsulation dot1Q 11
ip address 10.20.11.1 255.255.255.248
ipv6 address 2001:DB8:20:11::1/64The block above is trimmed to the subinterface, the full file is CustB-Hub.ios.
CustB has a third site, Spk2, attached to B-PE2 in SP-B. The subnet is a /29 so that Spk2 can use 10.20.11.3.
The Pseudowire
A pseudowire class is a set of pseudowire settings that the xconnect line points to with pw-class. Both PEs use the same one. It sets MPLS encapsulation and turns on the control word:
pseudowire-class VPWS_CB_CW
encapsulation mpls
control-wordThe control word is an optional 4-byte field between the MPLS labels and the customer’s Ethernet frame. Core routers that load-balance MPLS traffic look at the first 4 bits after the labels: 4 means IPv4, 6 means IPv6. Without a control word, those bits are the start of the destination MAC address, so a MAC that starts with 4 or 6 looks like an IP packet. The control word starts with 0, so the routers don’t mistake the Ethernet frame for IP:
The control word has other uses as well. It can carry a sequence number, and the far PE then drops frames that arrive out of order. A length field marks short frames that were padded, so the far PE can remove the padding. It also carries control bits for ATM and Frame Relay, and fragmentation bits for frames larger than the pseudowire MTU. Sequencing stays disabled on this pseudowire.
Each PE signals the control word with the C-bit in its LDP label advertisement for the pseudowire. If the two ends disagree, the pseudowire comes up without the control word. Without the control-word line, IOS-XE offers it and drops it when the other PE doesn’t use it. With the line on both PEs, both advertise Cbit: 1:
A-PE1#show mpls l2transport binding 2011
Destination Address: 10.1.0.6,VC ID: 2011
Local Label: 1517
Cbit: 1, VC Type: Ethernet, GroupID: 10
MTU: 1500, Interface Desc: VPWS E-Line VC 2011 -> CustB-Hub<->Spk1
VCCV: CC Type: CW [1], RA [2], TTL [3]
CV Type: LSPV [2]
Remote Label: 1614
Cbit: 1, VC Type: Ethernet, GroupID: 10
MTU: 1500, Interface Desc: VPWS E-Line VC 2011 -> CustB-Spk1<->Hub
VCCV: CC Type: CW [1], RA [2], TTL [3]
CV Type: LSPV [2]A pseudowire comes up only when both ends advertise the same MTU, 1500 here.
A-PE1 and A-PE2 are not directly connected, so the VC labels go over a targeted LDP session between their loopbacks:
A-PE1#show mpls ldp neigh 10.1.0.6
Peer LDP Ident: 10.1.0.6:0; Local LDP Ident 10.1.0.5:0
TCP connection: 10.1.0.6.40784 - 10.1.0.5.646
State: Oper; Msgs sent/rcvd: 29/28; Downstream
Up time: 00:13:54
LDP discovery sources:
Targeted Hello 10.1.0.5 -> 10.1.0.6, active, passive
Addresses bound to peer LDP Ident:
10.1.1.30 10.1.1.34 10.1.0.6 10.1.0.106CustB-Hub to CustB-Spk1
A ping from CustB-Hub to CustB-Spk1 enters the pseudowire at A-PE1 and rides Tunnel10 to A-PE2:
The two CEs are on one subnet across the pseudowire, so each CE has the other CE’s MAC address in its ARP table. From CustB-Hub:
CustB-Hub#show ip int br | i Ethernet0/1
Ethernet0/1 unassigned YES TFTP up up
Ethernet0/1.11 10.20.11.1 YES manual up up
CustB-Hub#ping 10.20.11.2 source Eth0/1.11
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.20.11.2, timeout is 2 seconds:
Packet sent with a source address of 10.20.11.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/2/3 ms
CustB-Hub#ping 2001:db8:20:11::2 source eth0/1.11
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:20:11::2, timeout is 2 seconds:
Packet sent with a source address of 2001:DB8:20:11::1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/2/6 ms
CustB-Hub#show arp | i 10.20.11.2
Internet 10.20.11.2 17 aabb.cc00.1510 ARPA Ethernet0/1.11
CustB-Hub#show ipv6 neigh Eth0/1
CustB-Hub#show ipv6 neigh Eth0/1.11
ND cache expire time is 14400 seconds
IPv6 Address Age Link-layer Addr State Interface
2001:DB8:20:11::2 0 aabb.cc00.1510 REACH Et0/1.11
FE80::A8BB:CCFF:FE00:1510 0 aabb.cc00.1510 REACH Et0/1.11From CustB-Spk1:
CustB-Spk1#ping 10.20.11.1 source Ethernet0/1.11
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.20.11.1, timeout is 2 seconds:
Packet sent with a source address of 10.20.11.2
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/2/3 ms
CustB-Spk1#ping 2001:db8:20:11::1 source Ethernet0/1.11
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:20:11::1, timeout is 2 seconds:
Packet sent with a source address of 2001:DB8:20:11::2
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/2/3 ms
CustB-Spk1#show arp | i 10.20.11.1
Internet 10.20.11.1 18 aabb.cc00.1410 ARPA Ethernet0/1.11What’s Next
The CustA L3VPN between HQ and Br1 still works over IPv4 and IPv6:
CustA-HQ#ping 10.10.0.2 source lo0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.0.2, timeout is 2 seconds:
Packet sent with a source address of 10.10.0.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/3 ms
CustA-HQ#ping 2001:db8:10::2 source lo0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8:10::2, timeout is 2 seconds:
Packet sent with a source address of 2001:DB8:10::1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/4/13 msThe next stage adds the EVPN-ELAN on VLAN 12 of the same Gi5 ports.
Leave a comment