Flow Control On Ethernet Interfaces; Vrrp; Hsrp - Cisco ASR 9000 Series Configuration Manuallines

Flow Control on Ethernet Interfaces

Jumbo frame support is automatically enable for frames that exceed the standard frame size. The default value
is 1514 for standard frames and 1518 for 802.1Q tagged frames. These numbers exclude the 4-byte FCS.
Flow Control on Ethernet Interfaces
The flow control used on 10-Gigabit Ethernet interfaces consists of periodically sending flow control pause
frames. It is fundamentally different from the usual full- and half-duplex flow control used on standard
management interfaces. On the Cisco ASR 9000 Series Routers both ingress and egress flow control are off
by default.

VRRP

The Virtual Router Redundancy Protocol (VRRP) eliminates the single point of failure inherent in the static
default routed environment. VRRP specifies an election protocol that dynamically assigns responsibility for
a virtual router to one of the VPN concentrators on a LAN. The VRRP VPN concentrator controlling the IP
addresses associated with a virtual router is called the master, and forwards packets sent to those IP addresses.
When the master becomes unavailable, a backup VPN concentrator takes the place of the master.
For more information on VRRP, see the Implementing VRRP chapter of Cisco ASR 9000 Series Routers IP
Addresses and Services Configuration Guide.

HSRP

Hot Standby Routing Protocol (HSRP) is a proprietary protocol from Cisco. HSRP is a routing protocol that
provides backup to a router in the event of failure. Several routers are connected to the same segment of an
Ethernet, FDDI, or token-ring network and work together to present the appearance of a single virtual router
on the LAN. The routers share the same IP and MAC addresses and therefore, in the event of failure of one
router, the hosts on the LAN are able to continue forwarding packets to a consistent IP and MAC address.
The transfer of routing responsibilities from one device to another is transparent to the user.
HSRP is designed to support non disruptive failover of IP traffic in certain circumstances and to allow hosts
to appear to use a single router and to maintain connectivity even if the actual first hop router they are using
fails. In other words, HSRP protects against the failure of the first hop router when the source host cannot
learn the IP address of the first hop router dynamically. Multiple routers participate in HSRP and in concert
create the illusion of a single virtual router. HSRP ensures that one and only one of the routers is forwarding
packets on behalf of the virtual router. End hosts forward their packets to the virtual router.
The router forwarding packets is known as the active router. A standby router is selected to replace the active
router should it fail. HSRP provides a mechanism for determining active and standby routers, using the IP
addresses on the participating routers. If an active router fails, a standby router can take over without a major
interruption in the host's connectivity.
HSRP runs on top of User Datagram Protocol (UDP), and uses port number 1985. Routers use their actual IP
address as the source address for protocol packets, not the virtual IP address, so that the HSRP routers can
identify each other.
For more information on HSRP, see the Implementing HSRP chapter of Cisco ASR 9000 Series Routers IP
Addresses and Services Configuration Guide.
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
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than the smallest MTU of all the networks in its path, that packet will be fragmented as necessary. This
process ensures that the originating device does not send an IP packet that is too large.
The Carrier Ethernet Model