Hi,   I have an SF300 switch and I'm trying to learn QoS by testing and configuring different QoS settings. There are 4 egress queues per each port. When I set the scheduler policy to weighted round robin (instead of strict priority mode) and test 2 sets of weights for egress ports, which are relatively equal, I see different results! For instance, I set weights 1,1,1,3  for queues in the first scenario and the egress queues' packets are coming out of port, likely respecting weights. But in the second scenario when I change the weights  into 3,3,3 and 9, without changing anything else, the egress direction of the port does not behave in compliance with the weights( the 4th queue, with the 9 weight in the second scenario, gets lower share  rather than first scenario)    Is it normal to see this behavior from SF300 switch?   Best, Amir   ... View more

Hi everyone!   I have an SF300 series switch which functions properly in mapping packet to egress queues by CoS value. My test scenario was this: I put one FastEthernet port and one GigabitEthernet port in One VLAN, then I sent two streams of data on Gigabit port, one with CoS=7 and another with CoS=0, each stream has 60 Mbps rate. Then I monitor FastEthernet port which has 100 Mbps bandwidth. the stream with CoS =7 was delivered completely without packet drop( 60 Mbps), but the second stream had packet drop(40 Mbps received)...So the switch is ok in the mapping of CoS to egress queues, but when I did this test by DSCP=46 and DSC=0, the switch behaves two streams equally with the same packet drop.Qo   I don't know where is the problem. The Switch explicitly says it supports DSCP to queues mapping. Could you please help?     here are some configurations:     qos advanced-mode trust dscp Dscp-queue map: d1 : d2 0 1 2 3 4 5 6 7 8 9 ------------------------------------- 0 : 01 01 01 01 01 01 01 01 01 01 1 : 01 01 01 01 01 01 02 02 02 02 2 : 02 02 02 02 03 03 03 03 03 03 3 : 03 03 03 03 03 03 03 03 03 03 4 : 04 04 04 04 04 04 04 04 03 03 5 : 03 03 03 03 03 03 03 03 03 03 6 : 03 03 03 03   ... View more

Hi, everybody!   I'm admin of a LAN and now I'm supposed to configure routing on it. I can define some VLANs on the network and also configure inter-VLAN routing between them(by SVIs or router on a stick). But when I associate each VLAN a subnet, what is the necessity of defining VLANs? Without VLANs, there are some subnets and I configure standard routing, like OSPF, between them and subnets, are separated from each other(like VLANs). So I can't recognize whether to use VLAN-based design or another. Could you please help me with this?   Best, Amir   ... View more

Hi, everyone!   Is it reasonable to use SF-300 switch as DHCP server in each subnet of an enterprise network? ( A ten-floor building and each floor is assigned to one subnet) I'm actually a little concerned about this device whether it functions as DHCP server properly or not. the link for the switch: https://www.cisco.com/c/en/us/support/switches/sf300-24p-24-port-10-100-poe-managed-switch-gigabit-uplinks/model.html#~tab-downloads   Thanks, Amir   ... View more

Hi everyone!   As I understood, " loopguard" is a proprietary Cisco feature and it seems to me that it has an important role in running STP. So ... I have two questions: 1- Does anyone know the equivalent of the loopgaurd feature in IEEE 802.1D standard? Does an IEEE standard support loopguard-like feature? 2- Does MSTP or RSTP or PVST or...  need loopgaurd feature too?   Thanks, Amir ... View more

Hi every one, I have been struggling a whole day to understand the real differences of Precise Time Protocol (IEEE 1588) and Synchronous Ethernet (syncE) and their role in the network. Greatly appreciated if you help me. So, my questions: 1- Does the PTP synchronize both time and frequency over the network? I've read in one of Cambium documents ( see the attachment please) that PTP is able to synchronize both time and frequency, but I can't understand how frequency get synchronized by packets? 2- In case synchronization is necessary, can one of these protocols synchronize network? for example, just using SyncE suffices for synchronization? Or both protocols are necessary? Maybe each protocol works in a specific and separate part of a network? 3- Is Grand Master clock (PTP term) the same as Primary Reference Clock ( SyncE term)? Are they one device in a network? Equivalently, can we have this mapping for all PTP devices and SyncE devices? Thanks, Amir ... View more

Hi,   I have two questions about the way a switch completes its MAC address table:   1. Suppose host A starts sending  packets for host B through a switch ( destination MAC addresses of packets are host B MAC address) and there is no response from host B to host A ( see the attachment please), I mean there is no ARP or CDP or similar protocols and host A just send layer 2 packets to the switch ( leaving higher layer headers empty ) . Does the switch "learn" to put host A packets on correct port for sending to host B or it will keep flooding them?    2. Is this scenario ( question number one scenario)  possible in a real and practical network? I mean that is it possible that no ARP or ARP-like protocols exists in a network and all the packets don't have any acknowledgment ( i.e. UDP)  to help L2 switches learn destination MAC addresses and stop flooding packets?   Best, Amir   ... View more