Interface Configuration Guide 7705 SAR Interfaces
Edition: 01 3HE 11011 AAAC TQZZA 97
When the network group encryption (NGE) feature is used, additional bytes due to
NGE packet overhead must be considered. Refer to the “NGE Packet Overhead and
MTU Considerations” section in the 7705 SAR Services Guide for more information.
3.2.12.2 IP Fragmentation
IP fragmentation is used to fragment a packet that is larger than the MTU of the
egress interface, so that the packet can be transported over that interface.
For IPv4, the router fragments or discards the IP packets based on whether the DF
(Do not fragment) bit is set in the IP header. If the packet that exceeds the MTU
cannot be fragmented, the packet is discarded and an ICMP message
“Fragmentation Needed and Don’t Fragment was Set” is sent back to the source IP
address.
For IPv6, the router cannot fragment the packet so must discard it. An ICMP
message “Packet too big” is sent back to the source node.
As a source of self-generated traffic, the 7705 SAR can perform packet
fragmentation.
Fragmentation can be enabled for GRE tunnels. Refer to the “GRE Fragmentation”
section in the 7705 SAR Services Guide for more information.
3.2.12.3 Jumbo Frames
Jumbo frames are supported on Ethernet ports except on the 8-port Ethernet
Adapter card (version 1).
The maximum MTU size for a jumbo frame on the 7705 SAR is 9732 bytes. The
maximum MTU for a jumbo frame may vary depending on the Ethernet
encapsulation type, as shown in Table 11. The calculations of the other MTU values
(service MTU, path MTU, and so on) are based on the port MTU. The values in
Table 11 are also maximum receive unit (MRU) values. MTU values are
user-configured values. MRU values are the maximum MTU value that a user can
configure on an adapter card that supports jumbo frames.
Table 11 Maximum MTU (or MRU) per Ethernet Encapsulation Type
Encapsulation Maximum MTU (bytes)
Null 9724
To Next Page
Loading...
