Questions tagged [gre]

Generic Routing Encapsulation is a tunnelling protocol, used to carry network layer protocols through encapsulation inside others.

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GRE over IPSec Transport vs. Tunnel Mode

I have a misunderstanding, in this article, Figure 4-9, in Transport Mode, first header (IPsec Hdr), is correct? Should not be GRE IP Hdr? https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/...
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GRE over IPsec problem

I'm trying to build a GRE Tunnel with IPSec encryption between two routers, but I keep getting error message saying "%CRYPTO-4-RECVD_PKT_NOT_IPSEC: Rec'd packet not an IPSEC packet..." Immediately I ...
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1answer
36 views

qos inside vpn, possible or not ? I read yes and no

I am wondering if possible to do QOS (or similar action) inside vpn tunnel to a cloud server. the goal is to reserved bandwith for voip traffic. I read that you can with GRE and other people said, ...
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1answer
213 views

How IPsec tunnel mode work without GRE

IPsec tunnel mode encrypt a whole IP packet and sends it as the payload of another IP packet. I have always used GRE as the encapsulation layer when doing IPsec encryption. However, how could I have ...
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1answer
28 views

Can a VPN tunnel between routers be built with different tunnel protocol on both ends?

I have two routers and the tunnel between them is up and working well. Router1 has GRE/IP as the protocol on its tunnel interface, and as for Router2 the tunnel interface is working with IPSEC/IP. Can ...
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1answer
58 views

Gre Tunnel issue

I've encountered an abnormal behavior of my GRE Tunnel between two routers Cisco. When I ping the remote physical IP of the tunnel, I reach it without any loss. But when I ping the remote Tunnel IP, I ...
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1answer
164 views

Scaling VXLAN tunnels in openvswitch

As we're creating a cluster of tens of KVM host nodes we've chosen openvswitch as our virtual network infrastructure. So we need to make isolated virtual networks between VMs on demand. I've seen ...
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1answer
229 views

Use cases for GRE over IPSEC

I'm trying to understand use cases for GRE over IPSEC. In the diagram below, each site uses GRE to encapsulate multicasts associated with OSPF. (There is still a requirement to configure SAs between ...
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1answer
41 views

Two channels between two switches

Is there a way to provide two physically diverse channels between two switches? I'm using two Cisco Catalysis 3560s, and I want to have two separate channels between them, with different access ...
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1answer
96 views

Encrypt Gre tunnel traffic

I have a gre tunnel between vyatta and juniper srx . I would like to encrypt the gre tunnel traffic if its possible. thanks Pratik
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33 views

Network Security Tunnel

In the Tunnel Interface, when I edit the tunnel information, it shows: Attributes Values Tunnel Source IF10 Tunnel Destination 1.0.0.1 Tunnel Mode GRE What does IF10 ...
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2answers
823 views

GRE-IPsec Tunnel between Cisco Router and a Linux Router

I am trying to create a GRE/IPsec tunnel between Cisco router and a Linux Router. The tunnel is UP and active, but when I do a "show crypto session" on the Cisco router the Active SA's keep on ...
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292 views

TTL, GRE tunnel

I need some advise on the TTL. Currently my application vendor sets TTL to be with value 1 and he should increase it. He is thinking about value of 10, but I'm not sure that this is enough: Assuming ...
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1answer
71 views

Is it possible to append custom data to every packet of a request? [closed]

For an end-to-site VPN, i.e. where a device (VPN client) is responsible for encapsulating the GRE packet, is it possible to send some custom data along with the GRE packet beyond just the standard ...
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1answer
243 views

How to use ACL to deny sending packages to the GRE tunnel?

I need to do a small lab. The topology is shown on the image below: What I need to do, is make static routing so all routers can ping each neighbour's physical interface, configure a GRE tunnel ...
2
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1answer
275 views

PPP CHAP Authentication password requirement

What is the requirement for CHAP authentication on a PPP interface? I thought both routers had to have the same password defined, such as below. r1> username r2 password demo r2> username r1 ...
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2answers
482 views

OSPF on tunnel interfaces

Can I keep different tunnel interfaces in different OSPF areas. Keep in mind that the physical interface is going to be the same
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3answers
304 views

Layer 3 tunnel with Dynamic IP address

I want to ask whether it is possible to configure Layer 3 Tunnel with the two end points/interfaces have dynamic IP address? If the interface IP change, the tunnel will have to be re-negotiated, is ...
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1answer
80 views

Qos implementation

I want to implement Qos on a GRE tunnel and want to give priority to a destination IP 1.1.1.1 of a system from our site using WAN link. I will match the traffic through an ACL in class-map in which ...
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1answer
89 views

Secure communication between multiple sites over Internet

Does anyone know what would be the best practice to securely connect 2 or more branches with HQ over the Internet, and to allow communication between all of them (so anyone can contact anyone) if I ...
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1answer
638 views

MPLS over GRE tunnel with Linux iproute2 [closed]

I'm trying to encapsulate IP packets in MPLS, transported over a GRE tunnel between two Linux hosts (a and b). a has 10.199.0.1 on GRE tunnel interface foo4, while b has 10.199.0.2 on GRE tunnel ...
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2answers
4k views

What is the difference between L2TP vs GRE

Can anyone clearly explain that what is the difference between L2TP and GRE tunnel? Is L2TPv3 Any different I am trying to understand where these protocol are used and why we use L2TP instead of ...
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1answer
479 views

GRE over IPSec vs L2TP over IPSEC

Every single VPN provider offers L2TP over IPSec. What is the reason GRE over IPSec is never offered ? Is there any downfall ? It seems to be exactly the same.
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1answer
810 views

Different tunnel modes (protected with ipsec)

I’m doing a connection of 2 sites in ipv6 over an ipv4 network. I thought to do a tunnel between this 2 sites and protect it with IPsec. But I saw there are different types of tunnels (by default GRE):...
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2answers
482 views

Site-to-Site VPN tunnel configuration

I remember in uni that we implemented VPN tunnels always on the border routers and then use GRE tunnels to connect between two remote subnets. I was always told that VPN tunnels need to know the ...
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2answers
91 views

Cisco IPSec questions on loopback0 and phase 2

ip multicast-routing crypto isakmp policy 2 encr 3des hash md5 authentication pre-share crypto isakmp key 123 address 1.7.129.10 ! crypto ipsec transform-set remotevpn esp-3des esp-md5-hmac ! ...
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547 views

Is a GRE tunnel sensitive to packet loss?

I tested a GRE tunnel on a lousy link, and all traffic seems lagging and slow, but when I switch to a healthy link, everything run smoothly. Is a GRE tunnel, in general, very sensitive to packet loss?...
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1answer
533 views

Regarding front door vrf concept

While reading up on front-door vrf concept here, i am just wondering , what if we made the network statements more precise/specific or used different subnets altogether, we would never have our tunnel ...
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1answer
314 views

Regarding Gre tunnel encapsulation

Please consider the attached image below: A GRE tunnel is set up between R1 and R4. Tunnel source is R1 interface having the IP address 172.16.0.1/16 Tunnel destination is R4 interface having the IP ...
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1answer
791 views

Regarding Multicast over the internet

I was going through the use cases of GRE tunnel and see that it is also used to carry multicast traffic over the internet.I understand that multicast IP belongs to class D address which is a public IP ...
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0answers
2k views

Tunnelling difference over VXLAN vs NVGRE vs GENEVE [closed]

Any bullet points that are most imp points when it comes differences between these three tunnellings VXLAN/NVGRE/GENEVE in networks. Found some notes here, anything that you may like to add would be ...
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1answer
732 views

More Fragment flag and Frag Offset field after GRE fragmentation

If the length of a packet by attaching GRE-IP header results in bigger size than router MTU, what happen on More Fragment Flag and Frag Offset field of that packet?
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3answers
4k views

GRE over IPsec between Juniper SRX100 and Fortigate 100D

I need assistance configuring VPN setup between Fortigate and Juniper devices (GRE over IPSec). I have the topology as follows: What I need to do is create a route-based IPSec tunnel between the ...
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2answers
717 views

Packet flow in GRE Tunnel

In the below image what would be the ip address in the outer ip header when packet goes from R1 to R2. If the ip address in the outer header is 172.16.0.1 , how does it travels the internet as its not ...
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1answer
1k views

Why source and destination addresses should match in GRE tunnel?

In a GRE tunnel, when R1 (public IP 172.16.0.1, tunnel address 10.0.0.1) sends a packet to R3 (public IP 172.16.0.6, tunnel address 10.0.0.2) and R3 receives it, the following happens: A packet is ...
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1answer
105 views

How would “looping” in GRE occur according to RFC 2784

RFC 2784 mentions: Care should be taken when forwarding such a packet, since if the destination address of the payload packet is the encapsulator of the packet (i.e., the other end of the tunnel), ...
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1answer
71 views

Why specify the source tunnel address?

http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/868-cisco-router-gre-ipsec.html Let me use the same example as in my previous question. R1(config)# interface Tunnel0 R1(config-if)#...
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1answer
2k views

Two GRE tunnels in one subnet

http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/868-cisco-router-gre-ipsec.html In the example above, R1: R1(config)# interface Tunnel0 R1(config-if)# ip address 172.16.0.1 255....
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2answers
303 views

Splitting Data and Voice by creating GRE tunnel for Data, using overhead for Voice

A client: 3 sites with L2 links to our Data Centre. I create L3 links by providing IP's both sides. I want to create a GRE tunnel over each link with seperate IPs in order to route Data over these new ...
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2answers
535 views

Support GRE tunneling router or firewall

I am new member of Network Engineering site! These days I am interested in GRE tunneling. I know that GRE is developed by CISCO and many routers produced by CISCO and Juniper support GRE tunneling. ...
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1answer
3k views

What is the difference between ip nhrp nhs and ip nhrp map?

These two commands seems similar when I configure a DMVPN Spoke. What is the difference? interface Tunnel1 ip address 192.168.88.2 255.255.255.248 no ip redirects **ip nhrp map 192.168.88.1 10.0.1....
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848 views

GRE tunnel(or even any tunnelling technique) between Alcatel 7750 and a Cisco Router

has anyone on here been able to successfully create a GRE tunnel or any kinda of tunnelling mechanism between an Alcatel router and a Cisco router. I've been struggling with this and for a while and ...
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167 views

Overlay network with GRE without spanning tree

I need to create an overlay network with potential of hundreds of servers (each is an hypervisor and running a open vswitch). I'm going to use ovswitch and connect each server to all other servers ...
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1answer
2k views

Transparent proxy (wccp and squid)

I am trying to solve problem about configuration of transparent proxy server. I don't have any configuration on devices, I have not started yet. Because of preparing and studying that topic. I am ...
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3answers
201 views

Can different networks connected by MPLS run the same OSPF area?

I was wondering if two different OSPF areas connected via an MPLS/GRE tunneled link run OSPF across them? May be keeping the interconnecting MPLS/GRE routers in OSPF backbone area 0?
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2answers
790 views

What problem does GRE solve?

As per the RFC, GRE (Generic Routing Encapsulation) specifies a protocol for encapsulation of an arbitrary protocol over another arbitrary network layer protocol. I don't think I understand ...
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1answer
650 views

DSCP trust over IPSec GRE

I have 2 branch offices connecting together via a metro-e and I'm running an ipsec gre tunnel between the 2 sites. routerA=branch1 routerB=branch2 WAN-------routerA----------|metroe|------------...
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3answers
14k views

Stuck at GRE troubleshooting with recursive route

As with my last question, I am learning for my CCNA exam and currently I am bashing my head against the wall, while trying to solve "7.2.2.4 Troubleshooting GRE" I'll explain the topology in a second....
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3answers
1k views

GRE Tunneling on Cisco IOS - Destination Address

What is the reason that you cannot set the tunnel's other side as destination address? Is this because it is virtual only? 192.168.1.0/30 is the subnet I'm using and this is my configuration: ...
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2answers
972 views

Alternatives to GRE for multicast over MPLS?

I have an application that requires multicast across our MPLS WAN, and had been using GRE tunnels to facilitate this until recently when I replaced some aging edge routers with HP L3 switches. To my ...