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Questions tagged [routing]

For questions about routing, the process of selecting to which network path traffic is sent. Consider using a more specific tag if your question is about a routing protocol like BGP or OSPF.

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Default Route Excluding VLAN on HP switch

I have configured HPE 5710 Layer 3 switch with multiple vlans. The Default Static Route displays it's interface as Vlan10, I am able to ping 8.8.8.8 from addresses in that vlan, including the switch ...
0 votes
1 answer
89 views

Static route weird behaviour

Hi, I am working with 4 routers: A B, P and C A and B have a P router between them that has an ospf neighborship with both. B is directly connected to router C. There's no routing protocol between B ...
0 votes
1 answer
123 views

Networking across campus with multiple ISPs

I currently have a campus that gets service from two ISP's that are each connected to their own router. The ISP's ingress and their routers are in different buildings on the campus. The buildings are ...
1 vote
1 answer
39 views

Why redistributed routes do not overwrite the original ones?

I am looking a bit into mutual redistribution and I am trying to find out how a router decides which routes to redistribute and why. R1 --ospf-- R2 --rip-- R3 Imagine the above scenario, in which R2 ...
7 votes
1 answer
6k views

Why is routing not working on my Dell N2048 switch

I am in the process of replacing some older Dell Powerconnect switches with a some Dell N2048 switches. While doing this I wanted to go ahead and segregate certain areas of my network using VLANs. ...
1 vote
1 answer
2k views

How to Run Static IP Through Comcast Business Class Modem to Router?

I apologize in advance for this kind of nebulous question, but I'm very stuck after many hours of trying and I need help. Here's what I have: Newest model of the Comcast Business Class Modem/Router ...
0 votes
1 answer
57 views

How do ISPs assign /29 public IP subnet on a single Ethernet/Fiber connection?

I recently found out the ISP provides a /28 public IP subnet to a business. I'm in the process of learning more about networking and find it interesting that 16 addresses are available through that ...
1 vote
1 answer
50 views

Why do routing tables and arp tables both require a field of interface?

Routing tables are queried using destination IP of a packet to get the next hop IP and to get the interface to send the packet through. But since the router will strip the ethernet header first and ...
2 votes
1 answer
413 views

How can I configure a Cisco router 4300 to allow internal server ip:80 to be accessed on public ip:4500

I have an internal web server on port 80. I need help commands maybe to configure port forwarding to access the server on my private network from a public IP Current running config interface ...
0 votes
2 answers
694 views

Cisco router on a stick with public ip wan (ISP)gateway

I am trying to create a router on a stick with an outside facing sub-interface with a public IP from an ISP. I have tried to configure NAT and routing but I just cant get to ping the internet. I'm ...
0 votes
1 answer
5k views

Destination NAT on Cisco ISR

I know how to perform regular overload PAT in my lab running sh ver Cisco IOS XE Software, Version 16.03.09 Cisco IOS Software [Denali], ISR Software (X86_64_LINUX_IOSD-UNIVERSALK9-M), Version 16.3.9, ...
0 votes
1 answer
55 views

Should a router behind the internet gateway run source NATing or masquerading if the gateway router is masquerading?

Edit: On a multi-router network, should a router (R2) behind the internet gateway (R1) run source NATing or masquerading if the gateway router is masquerading? At this time I can ssh from a host on ...
3 votes
2 answers
334 views

Colocation Rack Networking

I'm a sysadmin tasked with finding a managed service provider or networking contractor to build out our new colo space networking. I'm hoping to get some input to make sure I don't sound like an idiot ...
0 votes
1 answer
110 views

Problems with twice-NAT on Cisco 3548

I'm trying to get Twice-NAT working on a Cisco 3548 switch. I have a VRF set up with 2 L3 ports on it - Eth1/33 has ip address 20.20.255.250/16 and is nat inside Eth1/34 has ip address 10.10.1.211/24 ...
1 vote
2 answers
88 views

The use of VRF Lite

I have a quick question about VRF Lite. So I understand that VRF is a technology which allows the router to build multiple virtual routing tables which divide the network on L3 with each VRF table ...
-1 votes
1 answer
81 views

BGP - How are loops avoided when they are not caused by an AS_PATH cycle?

The standard answer I am seeing for how eBGP avoids routing loops is that eBGP routers of an AS will check each AS_PATH that is advertised to them and will discard the path if it contains their own AS ...
0 votes
2 answers
351 views

Connecting L3 and L2 switches with VLAN settings

I have 1 L3 switch with Static ip - 192.168.0.252 Two L2 switches Switch A - 192.168.0.250 Switch B - 192.168.0.251 I have created VLANs in L3 switches with 192.168.1.1 and 192.168.2.2 ips abd set it ...
1 vote
2 answers
323 views

bgp and routing

I need a bit of help understanding what is going on in my topology. I really want to understand why i can ping 1.1.1.1 from r4 but not from r5 or r6. Please help and advise me. Many thanks guys r1 ...
1 vote
2 answers
82 views

Is the routing table a control plane concept or a data plane concept?

I've always been told that the routing table is a control plane concept. You build this table, collect the routes, the way they were learned, their metrics, and so on. You then use this information to ...
1 vote
3 answers
4k views

Cannot create subinterface

I'm trying to connect 4 networks with 1 router, i created 2 sub-interfaces in the router, when i tried to create the 3rd sub-interface i got this output "%Cannot create sub-interface", this ...
8 votes
5 answers
6k views

Is rerouting possible in UDP?

So I am trying to understand routing for TCP and UDP segments. I have a couple of things that I am confused about: In TCP, is there any specification on how many packets would be dropped before a ...
5 votes
2 answers
7k views

difference between reverse, forwarding and return path on traceroute

As described on the title, I can't make difference between reverse, forwarding and return path, especially between reverse and return path. Also, how the RTT is affected by the reverse, forwarding ...
0 votes
0 answers
24 views

How to generate the netconf configuration for traffic enginerring with Segment routing from the CLI commands on Cisco IOS XR platofrm

I have below configurations to be pushed via netconf : Router Type :- IOS -XR CLI :- segment-routing traffic-eng segment-list ar4.BLB_ar7.BLB_c_10000_ep_1.2.3.4 index 1 mpls label 24001 index ...
1 vote
1 answer
1k views

IS-IS Interface Metric/Cost Calculation Issue in Juniper MX

I am facing a very strange issue with regard to IS-IS Interface Metric / Cost calculation in Juniper MX. We have configured a reference bandwidth of 1000G on all routers.This by definition means an ae ...
1 vote
0 answers
33 views

Is it possible to forward SMTP connections for various domains in the same server to different internal ports? [closed]

I have a server machine. If an incoming connection comes on https://abc.com:443, it's redirected to internal port :81 and if https://xyz.com:443, it's redirected to :82. This works fine. Now I have 2 ...
2 votes
1 answer
2k views

Sonicwall TZ105 Site to Site VPN Created can ping gateways but can't ping network from other site

Need help here Site B TZ105 x0 Lan 192.168.162.1 X1 WAN 64.x.x.x X2 LAN 10.0.3.1 Site A TZ300 X0 LAN 10.0.1.1 X1 WAN 69.x.x.x VPN tunnel set up as VPN SITE TO SITE and is Green From Site A I ...
3 votes
1 answer
125 views

Should I be using point-to-point or broadcast if I plan on using SVIs in IS-IS on Juniper?

Apologies in advance if this is super-basic question, still learning ISIS. I'm migrating from Cisco over to Juniper in an environment where all of the switches are running EIGRP, are on a 172.31.255.0/...
2 votes
1 answer
1k views

How to virtual-link between two different OSPF areas

Is there a way to connect routers via virtual-link between two different OSPF area?
0 votes
1 answer
57 views

Could address be omitted from packet in IPv4 if router is sending to / from that address?

Imagine an IPv4 packet routed like this: A -> Router1 -> Router2 -> B When constructing a packet per the structure, it seems A will have to include both source address (A) and destination ...
1 vote
1 answer
112 views

BGP: Are Virtual Internet Exchanges more efficient than normal internet transit?

There are a number of virtual internet exchanges that BGP peer over VPN links when local presence is not available. Given the IP encapsulation overhead, and the fact that these routes still cross the ...
1 vote
1 answer
81 views

Rip Routing Protocol

RIP routing protocol use the distance vector routing algorithm that mean each router will share the distance information,But how can this distance information help the router to know where to forward ...
2 votes
1 answer
83 views

OSPF - is the Designated Router the same thing as the Master Router?

Is it possible, to have a DR as a Slave Router? So here is my knowledge: The DR and the BDR are elected based on priority and then highest RID in an area, so every router can communicate with the DR ...
1 vote
1 answer
52 views

Nested Network with same IP Space

I have a router (Teltonika RUT) that is connected via its WAN port to a network (let's call it "Big"). The IP Space of the "Big" Network is 192.168.1.0/24 with the Gateway on 192....
1 vote
1 answer
547 views

How to block telnet access for one particular network from all networks except one using Extended ACL

Scenerio is given in the picture. I want to block all the networks except 192.168.5.128/25 from doing telnet of 192.168.5.0/25.
0 votes
1 answer
323 views

Inbound VPN connection and cascading routers: Who should act as server

I need a decision support for the configuration of incoming VPN connections. The setup consists of 2 cascaded routers. Router A (Zywall USG210) acts as front firewall and router B (Lancom EF1781) as ...
0 votes
2 answers
101 views

Connecting two different networks behind different firewalls [closed]

I have two LANs in the same building with different ISP and both behind different hardware firewalls connected to a switch like in the first picture bellow. Before, both LANs were connected through ...
2 votes
1 answer
513 views

Why I can't ping my switch Vlan99?

In the following network, I have configured every device but somehow I can't ping my Customer-PC and Technical-PC to PasirGudang-SW and Segamat-SW. The PCs can ping the other ip address just fine ...
2 votes
1 answer
65 views

How does the final next-hop router forward a frame to the destination device if the public IP address is that of its router

We know that all device’s connected to the same local network will have the same public IP address as each other, which belongs to their local router. So, since the IP packet’s destination address is ...
3 votes
1 answer
115 views

Computers on different subnets can't talk to each other

I'm teaching an introductory computer engineering course in HS and had students in the lab network together the computers they built in the hardware unit - I appreciate the irony of somebody teaching, ...
2 votes
5 answers
3k views

Do routers understand transport protocol?

We are taught about the difference between hubs, switches, and routers. A hub is a layer 1 device, it only knows layer 1 and doesn't care about layer 2 and above. Similarly, a switch is a layer 2 ...
1 vote
2 answers
1k views

Routing between SVI and routed port on router

How can I achieve reachability from vlan terminated on the L3 switch to routed port on the router, FW? F.E int vlan 10,50 are the SVI's on L3 switch vlan 10 - 10.0.10.254 /24 vlan 50 - 10.0.50.254 /24 ...
9 votes
5 answers
32k views

Do routers change MAC address of packets when forwarding

Lets say host A wants to send a packet to host B through R1(interface 1 then 2) and R2 (interface 3), so my questions is: When the packet is forwarded inside R1 (from interface 1 to interface 2), ...
1 vote
1 answer
66 views

Cisco BGP RTBH in EVPN fabric

I have Cisco basic EVPN fabric configuration in DC with two spine and couple of leafs using OSFP+iBGP for underlay fabric. My border leaf connected to my ISP using Vrf CUST. I want to configure RTBH ...
3 votes
1 answer
211 views

Juniper EX4200 Public Subnet Vlan Routing

We have a Juniper EX4200 which is connected via ge-0/0/0 trunk port to the providers router. We got our own vlan(id 250) and there are two public subnets routed on this vlan. Currently all our serves ...
0 votes
1 answer
265 views

Issue w/ Cisco router and failed NAT and static default route

I have a cisco router that is using a VRF to support a site to site VPN tunnel. I have added a second network to the router for non-VPN standard internet use. My problem is that my default static ...
1 vote
1 answer
176 views

Configure AAA on a router - Extended ACLs

How do I write a named extended ACL which will allow for traffic between a DNS from a LAN (IP address) to a DNS server at (IP address), ping from a host PC (IP address) to any destination and allow ...
0 votes
0 answers
87 views

intervlan routing on cisco L3 stacked switches

I am new to this and I am having a bit of a issue trying to successfully perform intervlan routing on a stacked L3 switche(s). I essentially have three SVIs with their corresponding VLANS ( i think) ...
1 vote
1 answer
421 views

Multiple GRE tunnels towards single host using anycast IP

I'm trying to build the following network architecture: Where clients try to connect to a backend server (e.g. SSH) by using a Public Anycast IP adddress (1.2.3.4), that routes the client to the ...
0 votes
1 answer
203 views

Can control plane and data plane be different in BGP?

I have heard that the BGP routes exchanged between the routers do not necessarily mean that the actual data path will follow the specified routes. How can the data path and control path be different ...
1 vote
1 answer
91 views

Can an application on two separate devices share a packet to similar resource?

Can packets requested for an image by an app on a phone be sent to same app on another phone by another user?

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