Need help?

Our experts have had an average response time of 13.52 minutes in October 2021 to fix urgent issues.

We will keep your servers stable, secure, and fast at all times for one fixed price.

Guest unable to reach host using macvtap interface

by | Apr 4, 2021

Wondering how to fix Guest unable to reach host using macvtap interface? We can help you.

Generally, guest virtual machines can communicate with other guests. But at times a guest will not be able to connect to the host machine after being configured to use a macvtap network interface.

Here at Bobcares, we get requests from our customers to fix similar issues of guest virtual machines as a part of our Server Management Services.

Today let’s see what causes this issue and how our Support Engineers fix this for our customers.

What makes the Guest unable to reach host using macvtap interface

When we configure a guest virtual machine to use a type=’direct’ network interface such as macvtap, despite having the ability to communicate with other guests and other external hosts on the network, the guest cannot communicate with its own host.

However, this is actually not an error as it is the defined behaviour of macvtap. Because of the way in which the host’s physical Ethernet is attached to the macvtap bridge, traffic into that bridge from the guests that is forwarded to the physical interface cannot be bounced back up to the host’s IP stack.

Additionally, traffic from the host’s IP stack that is sent to the physical interface cannot be bounced back up to the macvtap bridge for forwarding to the guests.

Methods to fix the issue:

Following are the two methods that our Support Engineers follow to fix this error:

 1. Creating a separate macvtap interface for the host

We can create a separate macvtap interface for host use and give it the IP configuration previously on the physical ethernet. In this way, the host would be an equal peer attached to the macvlap bridge and thus guest and host could communicate directly.

2. Using libvirt for creating an isolated network 

Use libvirt to create an isolated network and create a second interface for each guest virtual machine that is connected to this network. The host and guests can then directly communicate over this isolated network, while also maintaining compatibility with NetworkManager.

Following are the steps for creating an isolated network with libvirt

1. First, we need to add and save the following XML in the /tmp/isolated.xml file. If the 192.168.254.0/24 network is already in use elsewhere on our network, we can choose a different network.

...
<network>
<name>isolated</name>
<ip address='192.168.254.1' netmask='255.255.255.0'>
<dhcp>
<range start='192.168.254.2' end='192.168.254.254'/>
</dhcp>
</ip>
</network>
...

2.  Then create the network with the following command:

virsh net-define /tmp/isolated.xml

3. After that, we need to set the network to autostart with the following command:

virsh net-autostart isolated

4. And start the network with the following command:

virsh net-start isolated

5. Now, edit the configuration of each guest that uses macvtap for its network connection using the following command:

virsh edit name_of_guest

Add a new <interface> in the <devices> section similar to the following (note the <model type=’virtio’/> line is optional to include):

...
<interface type='network' trustGuestRxFilters='yes'>
<source network='isolated'/>
<model type='virtio'/>
</interface>

6. Finally, shut down, then restart each of these guests.

Since this new network is isolated to only the host and guests, all other communication from the guests will use the macvtap interface.

[Need Assistance? We are happy to help you!]

Conclusion

In short, we saw how our Support Engineers fix the issue with guests unable to reach the host using macvtap interface.

PREVENT YOUR SERVER FROM CRASHING!

Never again lose customers to poor server speed! Let us help you.

Our server experts will monitor & maintain your server 24/7 so that it remains lightning fast and secure.

GET STARTED

var google_conversion_label = "owonCMyG5nEQ0aD71QM";

0 Comments

Submit a Comment

Your email address will not be published. Required fields are marked *

Reviews

Privacy Preference Center

Necessary

Necessary cookies help make a website usable by enabling basic functions like page navigation and access to secure areas of the website. The website cannot function properly without these cookies.

PHPSESSID - Preserves user session state across page requests.

gdpr[consent_types] - Used to store user consents.

gdpr[allowed_cookies] - Used to store user allowed cookies.

PHPSESSID, gdpr[consent_types], gdpr[allowed_cookies]
PHPSESSID
WHMCSpKDlPzh2chML

Statistics

Statistic cookies help website owners to understand how visitors interact with websites by collecting and reporting information anonymously.

_ga - Preserves user session state across page requests.

_gat - Used by Google Analytics to throttle request rate

_gid - Registers a unique ID that is used to generate statistical data on how you use the website.

smartlookCookie - Used to collect user device and location information of the site visitors to improve the websites User Experience.

_ga, _gat, _gid
_ga, _gat, _gid
smartlookCookie

Marketing

Marketing cookies are used to track visitors across websites. The intention is to display ads that are relevant and engaging for the individual user and thereby more valuable for publishers and third party advertisers.

IDE - Used by Google DoubleClick to register and report the website user's actions after viewing or clicking one of the advertiser's ads with the purpose of measuring the efficacy of an ad and to present targeted ads to the user.

test_cookie - Used to check if the user's browser supports cookies.

1P_JAR - Google cookie. These cookies are used to collect website statistics and track conversion rates.

NID - Registers a unique ID that identifies a returning user's device. The ID is used for serving ads that are most relevant to the user.

DV - Google ad personalisation

IDE, test_cookie, 1P_JAR, NID, DV, NID
IDE, test_cookie
1P_JAR, NID, DV
NID
hblid

Security

These are essential site cookies, used by the google reCAPTCHA. These cookies use an unique identifier to verify if a visitor is human or a bot.

SID, APISID, HSID, NID, PREF
SID, APISID, HSID, NID, PREF