Administrator Guide

Handling of Switch-Initiated Traffic
When the control processor (CP) initiates a control packet, the following processing occurs:
● TCP/UDP port number is extracted from the sockaddr structure in the in_selectsrc call which is called as part of the
connect system call or in the ip_output function. If the destination TCP/UDP port number belongs to a configured
management application, then sin_port of destination sockaddr structure is set to Management EIS ID 2 so that route lookup
can be done in the management EIS routing table.
● To ensure that protocol separation is done only for switch initiated traffic where the application acts as client, only the
destination TCP/UDP port is compared and not the source TCP/UDP port. The source TCP/UDP port becomes a known
port number when the box acts as server.
● TFTP is an exception to the preceding logic.
● For TFTP, data transfer is initiated on port 69, but the data transfer ports are chosen independently by the sender and
receiver during initialization of the connection. The ports are chosen at random according to the parameters of the
networking stack, typically from the range of temporary ports.
● If route lookup in EIS routing table succeeds, the application-specific packet count is incremented. This counter is viewed
using the show management application pkt-cntr command. This counter is cleared using clear management
application pkt-cntr command.
● If the route lookup in the EIS routing table fails or if management port is down, then packets are dropped. The application-
specific count of the dropped packets is incremented and is viewed using the show management application pkt-
drop-cntr command. This counter is cleared using clear management application pkt-drop-cntr command.
● Packets whose destination TCP/UDP port does not match a configured management application, take the regular route
lookup flow in the IP stack.
● In the ARP layer, for all ARP packets received through the management interface, a double route lookup is done, one in the
default routing table and another in the management EIS routing table. This is because in the ARP layer, we do not have
TCP/UDP port information to decide the table in which the route lookup should be done.
● The show arp command is enhanced to show the routing table type for the ARP entry.
● For the clear arp-cache command, upon receiving the ARP delete request, the route corresponding to the destination
IP is identified. The ARP entries learned in the management EIS routing table are also cleared.
● Therefore, a separate control over clearing the ARP entries learned via routes in the EIS table is not present. If the ARP
entry for a destination is cleared in the default routing table, then if an ARP entry for the destination exists in the EIS table,
that entry is also cleared.
● Because fallback support is removed, if the management port is down or the route lookup in EIS table fails packets are
dropped. Therefore, switch-initiated traffic sessions that used to work previously via fallback may not work now.
Handling of Switch-Destined Traffic
● The switch processes all traffic received on the management port destined to the management port IP address or the front-
end port destined to the front-end IP address.
● If the source TCP/UDP port number matches a configured EIS or non-EIS management application and the source IP
address is a management Port IP address, then the EIS route lookup is done for the response traffic and hence is sent out of
the management port. In this case, the source IP address is a management port IP address only if the traffic was originally
destined to the management port IP.
● ICMP-based applications like ping and traceroute are exceptions to the preceding logic since we do not have TCP/UDP port
number. So if source IP address of the packet matches the management port IP address EIS route lookup is done.
● Management application packet counter is incremented if EIS route lookup succeeds and packet is sent out of the
management port.
● If route lookup in the EIS routing table fails or if the management port is down, then packets are dropped. The management
application drop counter is incremented.
● Whenever IP address is assigned to the management port, it is stored in a global variable in the IP stack, which is used for
comparison with the source IP address of the packet.
Internet Group Management Protocol (IGMP)
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