Initially, all IP traffic, except for DHCP packets, on the EFP configured for IPSG is blocked. After a client
receives an IP address from the DHCP server, or after static IP source binding is configured by the administrator,
all traffic with that IP source address is permitted from that client. Traffic from other hosts is denied. This
filtering limits a host's ability to attack the network by claiming a neighbor host's IP address.
The IPSG feature is supported on attachment circuits and EFPs. Currently, the IPSG feature is not supported
on pseudowires.
Note
Pseudowires
A pseudowire is a point-to-point connection between pairs of PE routers. Its primary function is to emulate
services like Ethernet over an underlying core MPLS network through encapsulation into a common MPLS
format. By encapsulating services into a common MPLS format, a pseudowire allows carriers to converge
their services to an MPLS network.
The following scale enhancements are applicable to ASR 9000 Enhanced Ethernet line card:
• Support for 128000 pseudowires within VPWS and VPLS
• Support for 128000 pseudowires across VPLS and VPWS instances
• Support for upto 512 pseudowires in a bridge
This scale enhancement is supported in hardware configurations where RSP3 and ASR 9000 Enhanced Ethernet
line cards are used. However, these enhancements are not applicable to the RSP2, ASR 9000 Ethernet Line
Card and Cisco ASR 9000 Series SPA Interface Processor-700 line cards.
Note
DHCP Snooping over Pseudowire
The Cisco ASR 9000 Series Routers provide the ability to perform DHCP snooping, where the DHCP server
is reachable on a pseudowire. The Pseudowire is considered as a trusted interface.
The dhcp ipv4 snoop profile {dhcp-snooping-profile1} command is provided under the bridge domain to
enable DHCP snooping on a bridge and to attach a DHCP snooping profile to the bridge.
Virtual Forwarding Instance
VPLS is based on the characteristic of virtual forwarding instance (VFI). A VFI is a virtual bridge port that
is capable of performing native bridging functions, such as forwarding, based on the destination MAC address,
source MAC address learning and aging, and so forth.
A VFI is created on the PE router for each VPLS instance. The PE routers make packet-forwarding decisions
by looking up the VFI of a particular VPLS instance. The VFI acts like a virtual bridge for a given VPLS
instance. More than one attachment circuit belonging to a given VPLS are connected to the VFI. The PE router
establishes emulated VCs to all the other PE routers in that VPLS instance and attaches these emulated VCs
to the VFI. Packet forwarding decisions are based on the data structures maintained in the VFI.
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
206
Implementing Multipoint Layer 2 Services
Pseudowires
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