Single vs Dual vs Multi-homed Network
You will often come across the terms Single Homed, Dual Homed, and Single/Dual multi-homed when talking about the ISP/BGP connections in a data center. These terms are nothing but design topologies used to distinguish how the POP is connected to one or multiple ISPs. Each of these topologies are different from the other and serves different purposes and must be chosen as per the requirement.
Let us know explore what are these ISP connections are and how they function. There are three types of homed networks, although the terms single-homed and multi-homed are the most commonly used.
Single-Homed Network
When a site (POP) establishes a connection with just one single ISP then the connection is called Single-Homed Network. Under this topology, the set-up uses a static/dynamic routes provided by the ISP which is then connected to the edge router of the POP.
The following graphical representation of this topology will give you a clear insight on how the connection is established
The only advantage of this type of setup is that it is highly cost effective. However, it is not safe as it does not provide any redundancy or backup. Any breakage in the link will cause disruption in the whole connection. This is fine for a site that does not depend heavily on Internet.
Dual-Homed Network
In a Dual-Homed Network connection, a site has two or more connection to the same ISP. Now this can be connected to either one or two edge routers (ISP or POP) where one link is primary and the other is secondary or backup. The other way a POP can use this topology is to load balance the traffic using both the links. This type of network also offers redundancy at the host side.
Let's see how this connection looks like
Multi-Homed Network
Multi-Homed Network connection is when the POP is connected to more than one ISP at the same time. This type of Network topology offer several benefits including redundancy and backup in case of failure (any one ISP). In such scenario where one of the ISP goes down, the system switches all the traffic to the other active ISP without any network downtime. Another huge benefit is that the POP can decide the best network path to route the traffic and offering high efficiency. One can take Multi-Homing a step further and offer Dual-Multihomed, where there are two connections to multiple ISPs. This topology offers the most redundancy.
Single Multi-Homed Network connection
Dual Multi-Homed Network Connection
Why Multi-Homed Network is so essential in today's world?
In comparison to Single and Dual Homed Network, a Multi-Homed offers much more features and advantages that can benefit a host as well as the client. Redundancy/Reliability and Performance are the two major factors a client looks for before choosing a service provider. Having Multi-Homed network offers high level of both Efficiency and Reliability for business. Therefore, to maintain the same level of network quality worldwide a host must partner with multiple carriers.
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Which is better screened host firewall or dual-homed firewall?
Which is better screened host firewall or dual-homed firewall?
For most purposes, the screened host architecture provides both better security and better usability than the dual-homed host architecture.
Is screened host firewall a type of firewall?
A firewall which is implemented using a firewall router and a proxy server, with the router acting as a front end to the server. The firewall router first screens off any accesses which are disallowed to a closed network, apart from Web page accesses and secure accesses to services such as email.
What is a screened host gateway?
Screened Host Gateway A screen host gateway is essentially a dual-homed gateway in which outbound traffic (from trusted to un-trusted) can move unrestricted. Incoming traffic must first be screened and then sent to the bastion host, like in a dual-homed gateway.
How does screen host architecture for firewall different from screened subnet firewall architecture which one of above offers more security?
Screened-host firewall architecture allows only a single line of defense against possible attack. With the screened-subnet firewall architecture is similar except that it has multiple bastion hosts and lies behind a packet filtering router.
Can a multi homed host act as a router?
A multihomed server acts as a host on multiple IP subnets. The server can sometimes have more than one network interface card and can act as a router. IP packets, including multicast packets, are routed between the interfaces.
What is another name for a dual-homed firewall?
Dual-homed is a general term for proxies, gateways, firewalls, or any server that provides secured applications or services directly to an untrusted network. Dual-homed hosts can be seen as a special case of bastion hosts and multi-homed hosts. They fall into the category of application-based firewalls.
Why is a bastion host the system most likely to be attacked?
The reason is simple: the bastion host is the machine most likely to be attacked because it’s the machine most accessible to the outside world. It’s also the machine from which attacks against your internal systems are most likely to come because the outside world probably can’t talk to your internal systems directly.
What is the difference between a screened host and a screened subnet?
Whereas the screened subnet firewall employs two screened routers to create three subnets, a screened host firewall employs only one screened router to define two subnets: an external network and an internal network.
What is the advantage and disadvantage of dual-homed topology?
A dual-homed topology provides redundancy. As shown in Figure 1-5, the spoke routers are dual-homed and redundantly attached to two hub routers across a WAN cloud. The disadvantage to dual-homed topologies is that they are more expensive to implement than a single-homed topology.
What is dual-homed gateway?
A dual-homed host (or dual-homed gateway) is a system fitted with two network interfaces (NICs) that sits between an untrusted network (like the Internet) and trusted network (such as a corporate network) to provide secure access.
Dual Homing «Двойная привязка»
Для обеспечения клиентам надёжной связи с Интернет требуется соединение минимум с двумя интернет-сервис провайдерами более высокого уровня. При этом требуется взаимодействие с ними с использованием протокола BGP и конфигурирования своей автономной системы. Поддержка протокола BGP требуется на граничных маршрутизаторах. Также для повышения надёжности может быть использован не одно устройство граничный маршрутизатор и BRAS, а несколько, резервирующих друг друга.
Резервирование шлюза по умолчанию, протокол VRRP
Большая часть клиентского программного обеспечения и оборудования способна работать с единственным адресом шлюза по умолчанию. Это создаёт проблему надёжности в случае отказа физического устройства, имеющим этот адрес. Для решения такой проблемы был создан протокол VRRP (Virtual Router Redundancy Protocol). Этот протокол позволяет двум и более физическим устройствам обрабатывать запросы на конкретный IP адрес. В каждый момент времени запросы обрабатываются одним из них. В случае отказа этого устройства остальные обнаруживают это, и обработка запросов продолжается одним из оставшихся устройств. Кроме резервирования шлюза по умолчанию протокол VRRP может быть полезен и для целей резервирования других сервисов.
Служебные технологии
Для снижения издержек при эксплуатации и ускорения поиска неисправностей очень полезными являются встроенные в коммутаторы средства диагностики. К ним можно отнести средства передачи информации об ошибках и неисправностях по протоколам SNMP и syslog, средства измерения параметров проходящего трафика и загрузки ресурсов при помощи RMON, средства анализа топологии сети при помощи протокола LLDP. Особенно полезными могут быть средства удалённой диагностики отдельных портов и присоединённых к ним кабелей 802.3ah Ethernet OAM.
Используемое оборудование и его преимущества
В описываемом решении предлагается использовать коммутаторы QTECH QSW-3900 для создании кольца агрегации, коммутаторы QSW-2900 для непосредственного подключения пользователей. В качестве BRAS и граничного маршрутизатора можно использовать продукцию Ericsson- Redback, например младшую модель Redback SE-100.
Мультисервисные коммутаторы QTECH
Коммутаторы QTECH для уровней доступа и агрегации, благодаря применению новейших стандартизованных протоколов и технологий, реализуют высокую сетевую безопасность с обеспечением гарантированного обслуживания для всех категорий пользователей и различных типов сервисов. Включая сервисы Реального Времени, VPN и другие. Ethernet коммутаторы QTECH созданы на современной аппаратной платформе в полном соответствии с требованиями операторов связи по надежности элементной базы, низкому электропотреблению, расширенному температурному диапазону, форм фактору.
Коммутаторы специально разработаны для мультисервисных сетей, поддерживают сотни различных сервисов единовременно, сервисные модели PPPoE Plus (для плавной миграции от DSL к MetroE технологиям) и DHCP авторизации (IPOE) с привязкой к порту доступа. Обеспечивают скорость сходимости менее 200 миллисекунд для безобрывного предоставления услуг телефонии и телевидения, классификацию и управление трафиком различных услуг по правилам провайдера (Selective QinQ & Selective VLAN), технологии защиты конфиденциальности информации (IP Source Guard, DAI, ARP Proxy), средства подавления штормов без блокирования полезного трафика, развитые средства сетевого мониторинга, включая SLA L2 (OAM CFM) QTECH QSW-2900 обеспечивает легкое подключение корпоративных клиентов с предоставлением VPN сервисов.