D-Link DWS-1008 Product Manual - Page 80

Configuring and Managing IP Interfaces and Services, MTU Support

Page 80 highlights

Configuring and Managing IP Interfaces and Services MTU Support Mobility System Software (MSS) supports standard maximum transmission units (MTUs) of 1514 bytes for standard Ethernet packets and 1518 bytes for Ethernet packets with an 802.1Q tag. MSS does not support changing of the MTU through software configuration, and MSS does not do path MTU discovery. Communication between DWS-1008 switches is supported over any path MTU, and the Mobility Domain itself can run over the minimum IP path MTU (PMTU). However, tunnels between two switches require a path MTU of at least 1384 bytes. This minimum MTU path is required because D-Link devices use IP tunnels to transport user traffic between switches and to transport user traffic and control traffic between switches and DWL-8220AP access points. Encapsulation of the packets for tunneling adds an additional 44 bytes to the packet headers, so MSS does fragment and reassemble the packets if necessary to fit within the supported MTUs. However, MSS does not support defragmentation except at the receiving end of an IP tunnel, and only to reassemble fragments created by another D-Link device for tunneling. If the path MTU between D-Link devices is less than 1384 bytes, a device in the path might further fragment or drop a tunneled packet. If the packet is further fragmented, the receiving switch will not be able to reassemble the fragments, and the packet is dropped. Configuring and Managing IP Interfaces Many features, including the following, require an IP interface on the DWS-1008 switch: • Management access through Telnet • Exchanging information and user data with other DWS-1008 switches in your network IP interfaces are associated with VLANs. At least one VLAN on a switch must have an IP interface to provide management access. Optionally, the other VLANs configured on the switch also can each have an IP interface. Each IP interface must belong to a unique, nonoverlapping IP subnet. D-Link DWS-1008 User Manual 61

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D-Link DWS-1008 User Manual
µ1
Configuring and Managing IP
Interfaces and Services
MTU Support
Mobility System Software (MSS) supports standard maximum transmission units (MTUs) of 1514 bytes
for standard Ethernet packets and 1518 bytes for Ethernet packets with an 802.1Q tag. MSS does
not support changing of the MTU through software configuration, and MSS does not do path MTU
discovery.
Communication between DWS-1008 switches is supported over any path MTU, and the Mobility Domain
itself can run over the minimum IP path MTU (PMTU). However, tunnels between two switches require
a path MTU of at least 1384 bytes.
This minimum MTU path is required because D-Link devices use IP tunnels to transport user traffic
between switches and to transport user traffic and control traffic between switches and DWL-8220AP
access points. Encapsulation of the packets for tunneling adds an additional 44 bytes to the packet
headers, so MSS does fragment and reassemble the packets if necessary to fit within the supported
MTUs. However, MSS does not support defragmentation except at the receiving end of an IP tunnel,
and only to reassemble fragments created by another D-Link device for tunneling.
If the path MTU between D-Link devices is less than 1384 bytes, a device in the path might further
fragment or drop a tunneled packet. If the packet is further fragmented, the receiving switch will not be
able to reassemble the fragments, and the packet is dropped.
Configuring and Managing IP Interfaces
Many features, including the following, require an IP interface on the DWS-1008 switch:
• Management access through Telnet
• Exchanging information and user data with other DWS-1008 switches in your network
IP interfaces are associated with VLANs. At least one VLAN on a switch must have an IP interface to
provide management access. Optionally, the other VLANs configured on the switch also can each have
an IP interface. Each IP interface must belong to a unique, nonoverlapping IP subnet.