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BigIron RX Series Configuration Guide
165
53-1002253-01
Configuring IP parameters
7
GRE IP tunnel
The BigIron RX allows the tunneling of packets of the following protocols over an IP network using
the Generic Router Encapsulation (GRE) mechanism as described in RFC 2784:
•
OSPF
•
BGP
•
IS-IS point-to-point
Using this feature, packets of these protocols can be encapsulated inside a transport protocol
packet at a tunnel source and delivered to a tunnel destination where it is unpacked and made
available for delivery.
Figure 6
describes the GRE header format.
FIGURE 6
GRE header format
Checksum – This field is assumed to be zero in this version. If set to 1 means that the Checksum
(optional) and Reserved (optional) fields are present and the Checksum (optional) field contains
valid information.
Reserved0 – Bits 6:0 of the field are reserved for future use and must be set to zero in transmitted
packets. If bits 11:7 of the field are non-zero, then a receiver must discard the packet unless RFC
1701 is implemented. This field is assumed to be zero in this version.
Ver – This field must be set to zero. This field is assumed to be zero in this version.
GRE MTU configuration considerations
The default value of IP GRE tunnel MTU is 1476 bytes. The MTU of the GRE tunnel is compared with
the outgoing packet before the encapsulation is done. After the encapsulation, the packet size
increases by 24 bytes. If a user wants to change the GRE tunnel MTU, the MTU should be at least
24 bytes less than the IP MTU of the outgoing interface. Otherwise, the size of the encapsulated
packet will exceed the IP MTU of the outgoing interface. In that case, the packet is dropped if the
DF (Do-Not-Fragment) bit is set in the original IP packet, otherwise, the packet is sent to CPU for
fragmentation.
NOTE
The encapsulated packets sent on a GRE tunnel have the DF bit set. Setting a GRE tunnel MTU to
be greater than 1476 will cause the encapsulated packet to be greater than 1500 bytes. This may
cause the transit routers to drop the encapsulated packet if that transit router's IP MTU is 1500
bytes (a typical default MTU value) since transit routers can not fragment a GRE packet.
Configuring a GRE IP tunnel
To configure a GRE IP Tunnel, the following parameters must be configured:
•
Tunnel interface
•
Source Address for the Tunnel
•
Destination address for the Tunnel
Checksum
Reserved0
Ver
Protocol Type Checksum
(optional)
Reserved
(optional)
1 bit
12 bits
3 bits
16 bits
16 bits
16 bits
Содержание BigIron RX Series
Страница 100: ...24 BigIron RX Series Configuration Guide 53 1002253 01 Logging on through the Web Management Interface 2 ...
Страница 192: ...116 BigIron RX Series Configuration Guide 53 1002253 01 Configuring authentication method lists 4 ...
Страница 228: ...152 BigIron RX Series Configuration Guide 53 1002253 01 Enabling WAN PHY mode support 6 ...
Страница 312: ...236 BigIron RX Series Configuration Guide 53 1002253 01 Displaying IP information 7 ...
Страница 356: ...280 BigIron RX Series Configuration Guide 53 1002253 01 Resetting LLDP statistics 9 ...
Страница 402: ...326 BigIron RX Series Configuration Guide 53 1002253 01 Transparent firewall mode 11 ...
Страница 432: ...356 BigIron RX Series Configuration Guide 53 1002253 01 SuperSpan 12 ...
Страница 500: ...424 BigIron RX Series Configuration Guide 53 1002253 01 MRP CLI example 14 ...
Страница 580: ...504 BigIron RX Series Configuration Guide 53 1002253 01 Configuring multicast traffic engineering 18 ...
Страница 591: ...BigIron RX Series Configuration Guide 515 53 1002253 01 Displaying traffic reduction 19 ...
Страница 592: ...516 BigIron RX Series Configuration Guide 53 1002253 01 Displaying traffic reduction 19 ...
Страница 598: ...522 BigIron RX Series Configuration Guide 53 1002253 01 Viewing Layer 2 ACLs 20 ...
Страница 656: ...580 BigIron RX Series Configuration Guide 53 1002253 01 Trunk formation 22 ...
Страница 754: ...678 BigIron RX Series Configuration Guide 53 1002253 01 Displaying RIP filters 24 ...
Страница 814: ...738 BigIron RX Series Configuration Guide 53 1002253 01 Displaying OSPF information 25 ...
Страница 932: ...856 BigIron RX Series Configuration Guide 53 1002253 01 Generalized TTL security mechanism support 26 ...
Страница 980: ...904 BigIron RX Series Configuration Guide 53 1002253 01 Clearing IS IS information 28 ...
Страница 1000: ...924 BigIron RX Series Configuration Guide 53 1002253 01 Using secure copy 30 ...
Страница 1088: ...1012 BigIron RX Series Configuration Guide 53 1002253 01 IP source guard 35 ...
Страница 1108: ...1032 BigIron RX Series Configuration Guide 53 1002253 01 Reading CDP packets 37 ...
Страница 1126: ...1050 BigIron RX Series Configuration Guide 53 1002253 01 Clearing sFlow statistics 39 ...
Страница 1140: ...1064 BigIron RX Series Configuration Guide 53 1002253 01 802 1s Multiple Spanning Tree Protocol 40 ...
Страница 1324: ...1248 BigIron RX Series Configuration Guide 53 1002253 01 Displaying OSPFv3 information 48 ...
Страница 1363: ...BigIron RX Series Configuration Guide 1287 53 1002253 01 Continuous System Monitor 51 ...
Страница 1364: ...1288 BigIron RX Series Configuration Guide 53 1002253 01 Continuous System Monitor 51 ...
Страница 1404: ...1328 BigIron RX Series Configuration Guide 53 1002253 01 Commands That Require a Reload D ...
Страница 1458: ...1382 BigIron RX Series Configuration Guide 53 1002253 01 VSRP E ...