Brocade Communications Systems ICX 7450 series User Manual

GRE packet structure and header format
FIGURE 13 GRE encapsulated packet structure
FIGURE 14 GRE header format
The GRE header has the following elds:
• Checksum - 1 bit. This eld is assumed to be zero in this version. If set to 1, this means that the Checksum (optional) and
Reserved (optional) elds are present and the Checksum (optional) eld contains valid information.
• Reserved0 - 12 bits. If bits 1 - 5 are non-zero, then a receiver must discard the packet unless RFC 1701 is implemented. Bits
6 - 12 are reserved for future use and must be set to zero in transmitted packets. This eld is assumed to be zero in this
version.
• Ver - 3 bits. The GRE protocol version. This eld must be set to zero in this version.
• Protocol Type - 16 bits. The Ethernet protocol type of the packet, as dened in RFC 1700.
• Checksum (optional) - 16 bits. This eld is optional. It contains the IP checksum of the GRE header and the payload packet.
• Reserved (optional) - 16 bits. This eld is optional. It is reserved for Brocade internal use.
Path MTU Discovery support
Brocade IronWare software supports the following RFCs for handling large packets over a GRE tunnel:
• RFC 1191, Path MTU Discovery
• RFC 4459, MTU and Fragmentation Issues with In-the-Network Tunneling
IPv4 point-to-point GRE tunnels
FastIron Ethernet Switch Layer 3 Routing
53-1003627-04 103

Brocade Communications Systems ICX 7450 series Specifications

General

Brand	Brocade Communications Systems
Model	ICX 7450 series
Category	Switch
Language	English