
•
Assign a static route to point to the management interface or forwarding router.
CONFIGURATION mode
management route
ip-address mask
{
forwarding-router-address
| ManagementEthernet
slot/
port
}
Example of the
show ip management-route
Command
To view the configured static routes for the management port, use the
show ip management-route
command in EXEC
privilege mode.
Dell#show ip management-route
Destination Gateway State Route Source
----------- ------- ----- ------------
10.16.0.0/16 ManagementEthernet 1/1 Connected Connected
172.16.1.0/24 10.16.151.4 Active Static
IPv4 Path MTU Discovery Overview
The size of the packet that can be sent across each hop in the network path without being fragmented is called the path maximum
transmission unit (PMTU). This value might vary for the same route between two devices, mainly over a public network, depending
on the network load and speed, and it is not a consistent value. The MTU size can also be different for various types of traffic sent
from one host to the same endpoint.
Path MTU discovery (PMTD) identifies the path MTU value between the sender and the receiver, and uses the determined value to
transmit packets across the network. PMTD, as described in RFC 1191, denotes that the default byte size of an IP packet is 576. This
packet size is called the maximum transmission unit (MTU) for IPv4 frames. PMTD operates by containing the do not fragment (DF)
bit set in the IP headers of outgoing packets. When any device along the network path contains an MTU that is smaller than the size
of the packet that it receives, the device drops the packet and sends an Internet Control Message Protocol (ICMP) Fragmentation
Needed (Type 3, Code 4) message with its MTU value to the source or the sending device. This message enables the source to
identify that the transmitted packet size must be reduced. The packet is retransmitted with a lower size than the previous value. This
process is repeated in an interactive way until the MTU of the transmitted packet is lower or equal to the MTU of the receiving
device for it to obtain the packet without fragmentation. If the ICMP message from the receiving device, which is sent to the
originating device, contains the next-hop MTU, then the sending device lowers the packet size accordingly and resends the packet.
Otherwise, the iterative method is followed until the packet can traverse without being fragmented.
PMTD is enabled by default on the switches that support this capability. To enable PMTD to function correctly, you must enter the
ip unreachables
command on a VLAN interface to enable the generation of ICMP unreachable messages. PMTD is supported
on all the layer 3 VLAN interfaces. Because all of the Layer 3 interfaces are mapped to the VLAN ID of 4095 when VLAN sub-
interfaces are configured on it, it is not possible to configure unique layer 3 MTU values for each of the layer 3 interfaces. If a VLAN
interface contains both IPv4 and IPv6 addresses configured on it, both the IPv4 and IPv6 traffic are applied the same MTU size; you
cannot specify different MTU values for IPv4 and IPv6 packets.
Using the Configured Source IP Address in ICMP Messages
ICMP error or unreachable messages are now sent with the configured IP address of the source interface instead of the front-end
port IP address as the source IP address. Enable the generation of ICMP unreachable messages through the
ip unreachable
command in Interface mode. When a ping or traceroute packet from an endpoint or a device arrives at the null 0 interface configured
with a static route, it is discarded. In such cases, you can configure Internet Control Message Protocol (ICMP) unreachable
messages to be sent to the transmitting device.
Configuring the ICMP Source Interface
You can enable the ICMP error and unreachable messages to contain the configured IP address of the source device instead of the
previous hop's IP address. This configuration helps identify the devices along the path because the DNS server maps the loopback IP
address to the host name, and does not translate the IP address of every interface of the switch to the host name.
406
IPv4 Routing
Summary of Contents for S4048-ON
Page 1: ...Dell Configuration Guide for the S4048 ON System 9 9 0 0 ...
Page 146: ...Figure 14 BFD Three Way Handshake State Changes 146 Bidirectional Forwarding Detection BFD ...
Page 522: ...Figure 87 Configuring Interfaces for MSDP 522 Multicast Source Discovery Protocol MSDP ...
Page 523: ...Figure 88 Configuring OSPF and BGP for MSDP Multicast Source Discovery Protocol MSDP 523 ...
Page 528: ...Figure 91 MSDP Default Peer Scenario 1 528 Multicast Source Discovery Protocol MSDP ...
Page 529: ...Figure 92 MSDP Default Peer Scenario 2 Multicast Source Discovery Protocol MSDP 529 ...
Page 530: ...Figure 93 MSDP Default Peer Scenario 3 530 Multicast Source Discovery Protocol MSDP ...
Page 633: ...Policy based Routing PBR 633 ...
Page 777: ...Figure 119 Single and Double Tag TPID Match Service Provider Bridging 777 ...
Page 778: ...Figure 120 Single and Double Tag First byte TPID Match 778 Service Provider Bridging ...