In router you can choose to manually set the ‘passive-interface’ command on the interfaces where adjacency is not desired. The interface address that you specify as passive appears as a stub network in the OSPF domain. OSPF routing information is neither sent nor received through the specified device interface. Passive interface can be configured in [...]
The Virtual Switching System (VSS) is a clustering technology that combines two Cisco Catalyst 4500 or 6500 Series into a single virtual switch. In a VSS, the data plane of both clustered switches is active at the same time in both chassis. VSS members are connected by virtual switch links (VSLs) using standard Gigabit or [...]
If a static route is configured for the network to the null0 interface, the packets will be dropped without the ICMP message or without having to configure an access list to block/deny traffic. This interface is always up and can never forward or receive traffic and any encapsulation will always fail. The null interface provides [...]
Gateway Load Balancing Protocol (GLBP) provides redundancy for IP networks, ensuring that user traffic immediately and transparently recovers from first hop router failures, while allowing packet load sharing between a group of redundant routers. GLBP provides load balancing over multiple routers (gateways) using a single virtual IP address and multiple virtual MAC addresses. Each host [...]
There are two ways of authentication in OSPF. 1) Clear text authentication 2) MD5 authentication 1) Clear text authentication Area based authentication Cisco_Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Cisco_Router(config)#interface f0/0 Cisco_Router(config-if)#ip ospf authentication-key [email protected] Cisco_Router(config-if)#exit Cisco_Router(config)#router ospf 100 Cisco_Router(config-router)#area 2 authentication Cisco_Router(config-router)#exit Interface based authentication Cisco_Router(config)#int fa0/0 Cisco_Router(config-if)#ip ospf authentication [...]
To check the connectivity we can use the IP SLA feature in Cisco IOS which will be constantly pinging the internet address as soon as the icmp check will fail it will change the priority of the route so the traffic will get out through the other link. First we create our IP SLA cinfig. [...]
BGP (Border Gateway Protocol ) supports authentication using the md5 (message digest 5) algorithm. For authentication to be successful md5 authentication should be configured on both sides. When authentication is enabled when any TCP segment belonging to BGP exchanged between peers is accepted only if the authentication is successful. router bgp 100 no synchronization bgp [...]
You can configure data and voice vlan on the same port. You can’t configure the two access vlans on single port. When you configure the data & voice vlan on single port in that scenario. From the switch port first cable goes to voip phone. VOIP phone has two port one for the input and [...]
OSPF routers on multiaccess segments sync their databases with their Designated Router (DR) or a Backup Designated Router (BDR) only. The OSPF status between two routers transitions to Full only if at least one of them is a DR or a BDR. The state remains Two-way between a pair of routers if both routers are drothers.
Usually passive interface command is used in routing protocols to accept information from neighbors but prevent it from sending information to neighbors But in case of EIGRP (Enhanced Interior Gateway Routing Protocol) it is exactly opposite.EIGRP discovers neighbours using the hello packets,before accepting routes and installing them in the routing table. Hello messages are usually [...]
If there are multiple EIGRP and OSPF neighborship flap over the GRE tunnel what could be the problem and how would solve it?
If in the logging you are getting the error message %TUN-5-RECURDOWN: Tunnel0 temporarily disabled due to recursive routing It means that GRE Router tunnel has found a recursive routing problem. The symptoms of this issue include the continous flapping of tunnel interface as well as EIGRP,OSPF & BGP neighbours when neighbours are over the GRE. [...]
-If there is a data center outage or power outage, both vPC peers consisting of Nexus 7000 Switches are down. Sometimes, only one of the peers can be restored. Since the other Nexus 7000 is still down, vPC peer-link as well as vPC peer-keepalive link are also down. In this scenario, vPC will not come [...]
If Border Gateway Protocol (BGP) is not propagating any internal BGP (iBGP) learned routes to another iBGP peer because it requires a full iBGP mesh within the Autonomous System (AS). To overcome this issue you can configure BGP router as a route reflector By configuring a BGP router to be a route reflector, a full [...]
How to configure ACLs that permit only established connections and deny all traffic sourced from the external network
Adding the established keyword at the end of access-list indicates that packets belong to an existing connection if the Transmission Control Protocol (TCP) datagram has the Acknowledgment (ACK) or Reset (RST) bit set. access-list 110 permit tcp any any established When you add this make sure you enable DNS otherwise the url will not able [...]
In order to prevent Enhanced Interior Gateway Routing Protocol (EIGRP) updates from overwhelming the interface, Cisco IOS provides controls how much bandwidth it can consume on the physical interface. By default, EIGRP limits itself to using no more than 50 percent of the interface bandwidth. Although, this is not very significance on high speeds like [...]
If BGP is used in multihoming scenario then primary link gets fail, after how long traffic will be shifted to secondary link?
By default, fast external failover is enabled for eBGP neighbor. So when the egress interface fails, it immediately bring down the BGP session and next best path will be selected. if you have it disabled, it will rely on the BGP holdtimer.
In the multihomed environment load balancing is not an option because BGP select only one best path to destination when the BGP routes are learned from different AS’s.To achieve this we need to setup a better metric for the routers in the range 0.0.0.0 to 22.214.171.124 that are learned from ISP A and better metric [...]
There are three types of BGP Routing tables: a) Adj-RIB-in b) Adj-RIB-out c) Loc-RIB Adj-RIB-in stores the unprocessed information received from its peers. Here the best path selection occurs as per BGP attributes and after conformation path is entered into the local bgp table i.e Loc-RIB. From the local RIB table it conform the next-hop [...]
EIGRP can utilize 5 separate metrics to determine the best route to a destination: Bandwidth (K1) Load (K2 Delay of the Line (K3 Reliability (K4) MTU (K5) By default, only Bandwidth and Delay of the Line are used
Conditions to form EIGRP neighbors -It must receive HELLO PACKET from neighbor router -EIGRP AS number should be same -Must have identical K-values or Metric -Adjacencies will not form unless the primary IP addresses on connecting interfaces are on the same subnet.
SoO for BGP is “linked” to CE-neighbor. So, when a prefix needs to be advertised to a CE neighbor, we check the SoO of the prefix with the SoO of the BGP neighbor. For anything else, it is linked to interface. The configuration can be done in four ways –“route-map in” on CE BGP neighbor [...]
EIGRP uses AS (Autonomous system) number ranging from 1-65535 to identify collection of routers that share same information. EIGRP have less convergent time and is more efficient EIGRP supports both auto and manual route summarization Supports multiple routed protocols like IP ,IPX and apple talks EIGRP converges rapidly in the event of link failure EIGRP [...]
Below are the basic BGP timers Keepalive timer- 60 seconds Hold-down timer-3xkeepalive or 180seconds Advertisement interval- 30 seconds for eBGP peers and 0 seconds for iBGP peers Scan timer-60 seconds Did i miss anything please let me know through Setting->Feedback option
In the BGP the current versions i.e BGP-4 version supports CIDR
Private VLAN is a layer 2 network structure which an extension of the common VLAN technology. Within a Private VLAN domain there are three very different port designations exist. Each port designation has its own unique set of rules, which regulate a connected endpoint’s ability to communicate with other endpoints connected to ports within the [...]
5 networks route update RIP receives at once.
To set up the SUP engine redundancy one must have the same version of iOS. Once Sup engine redundancy is configured one switch will act as Active Sup and the other will act as standby sup engine Cisco6500(config)# redundancy Cisco6500(config-red)#keepalive-enable Cisco6500(config-red)#mode sso Cisco6500(config-red)#main-cpu Cisco6500(config-red-main-cpu)#auto-sync running-config SSO (Stateful Switch over) mode means it will sync the [...]
TCP is a connection-oriented protocol both ends of a connection keep strict track of all data transmitted, so that any lost or jumbled segments can be retransmitted or reordered as necessary to maintain reliable transport. To compensate for limited buffer space (where received data is temporarily stored until the appropriate application can process it), TCP [...]
There are two access-lists are allowed per interface. One in Inbound direction and other in the Outbound direction.
Cisco router generates a source quench only if it doesn’t have the buffer space needed to queue the packet. If the router can not queue the routed packet onto the output interface’s queue, it generates a source quench and registers an output drop against the output interface. If the router is not congested then it [...]
PAgP Port Aggregation Protocol (PAgP) is a Cisco proprietary protocol used for automated logical aggregation of Ethernet switch ports. PAgP has two modes Auto this mode sets the interface to respond to PAgP negotiation packets, but the interface will start negotiations on its own. Desirable this mode sets the interface to actively attempt to negotiate [...]
HSRP * Cisco proprietary * 1 Active & 1 standby router & 1 or more listening routers * use virtual ip address as gateway * hello 3 sec & holddown timer 10 sec * we can enable preempt manually (standby 1 preempt) 6) multicast at:126.96.36.199 (ver1), multicast at:188.8.131.52 (ver2). Both versions use udp port 1985 [...]
n7010# show incompatibility-all system bootflash:n7000-s1-dk184.108.40.206.bin ‘show incompatibility system’ shows configuration incompatibilities between the running system image and an another system image prior to downgrading/upgrading the Cisco NX-OS software.
In a 48 port switch if there are 5 vlans. There will be how many collision domains & broadcast domains
There will be 48 collision domains because every port on switch is collision domain. There will be 5 Broadcast domain as each vlans is broadcast domains.
When enabled globally, BPDU guard has these attributes: *If a BPDU is recieved by the port it will fall-back to normal STP operation (instead of Portfast) and go through the normal STP states When enabled on interface, BPDU guard has these attributes: *It will err-disable the port Exclusive promotion for our users checkout the 70% [...]
When enabled globally, BPDU filtering has these attributes: *It affects all operational PortFast ports on switches that do not have BPDU filtering configured on the individual ports. *If BPDUs are seen, the port loses its PortFast status, BPDU filtering is disabled, and the STP sends & receives BPDUs on the port as it would with [...]
BPDU’s are the messages exchanged between switches to calculate the spanning tree topology.Bridge Protocol Data Units (BPDU’s) frames contain information regarding the Switch ID, originating switch port, MAC address, switch port priority, switch port cost etc. Bridge Protocol Data Units (BPDU’s) frames are sent out as multicast messages regularly at multicast destination MAC address 01:80:c2:00:00:00. [...]
* Etherchannel * Stackwise * VSS (Virtual Switching System) * HSRP (Hot Standby Routing Protocol) If you want to add more in this answer you can send your feedback to us from Settings->Feedback CCNA Routing & Switching by Wendell Odom is perfect way to prepare for CCNA. Checkout the book on Amazon.in Amazon.com
In Cisco 6500 you can check the backplane utilisation using the command ‘show catalyst6000 traffic-meter’ ______________snip_______ sh catalyst6000 traffic-meter traffic meter = 10% peak = 25% at 01:23:17 CST Fri Sep 4 2014 ___________snip_________
The main difference is -6500-E chassis offers enhancements to support the 67XX and the 68XX series linecards. -6500-E chassis offer enhancements which increase the overall system power capacity for Power over Ethernet (PoE) port density scalability.